Engaging Senses in Devotional service

Lord Rshabha Dev's teachings

SB 5.5.27
The true activity of the sense organs — mind, sight, words and all the knowledge-gathering and working senses — is to engage fully in My service. Unless his senses are thus engaged, a living entity cannot think of getting out of the great entanglement of material existence, which is exactly like Yamarāja’s stringent rope.

Sense Gratification makes the body weak and reduces life span

Srila Prabhupada's Purport 4.27.24

(Narada Muni advises KalaKanya (Jara- old age) to marry the King of the Yavanas)

The words yavanānām ṛṣabham refer to the King of the Yavanas. The Sanskrit words yavana and mleccha apply to those who do not follow the Vedic principles. According to the Vedic principles, one should rise early in the morning, take bath, chant Hare Kṛṣṇa, offer maṅgala-ārati to the Deities, study Vedic literature, take prasāda and engage in dressing and decorating the Deities. One must also collect money for the temple expenditures, or if one is a householder he must go to work in accordance with the prescribed duties of a brāhmaṇa, kṣatriya, vaiśya orśūdra. In this way one should live a life of spiritual understanding, and this is the Vedic way of civilization. One who does not follow all these rules and regulations is called a yavana or mleccha. One should not mistakenly think that these words refer to certain classes of men in other countries. There is no question of limitation according to nationalism. Whether one lives in India or outside of India, he is called a yavana or mleccha if he does not follow the Vedic principles. One who does not actually follow the hygienic principles prescribed in the Vedic rules and regulations will be subjected to many contagious diseases. Because the students in this Kṛṣṇa consciousness movement are advised to follow the Vedic principles, they naturally become hygienic.

If a person is Kṛṣṇa conscious, he can work like a young man even if he is seventy-five or eighty years old. Thus the daughter of Kāla (Time) cannot overcome a Vaiṣṇava. Śrīla Kṛṣṇadāsa Kavirāja Gosvāmī engaged in writingCaitanya-caritāmṛta when he was very old, yet he presented the most wonderful literature about the activities of Lord Caitanya. Śrīla Rūpa Gosvāmī and Sanātana Gosvāmī began their spiritual lives at a very old age — that is, after they retired from their occupations and family lives — yet they presented many valuable literatures for the advancement of spiritual life.

.......

Because a devotee rigidly follows the instructions of Nārada Muni, he has no fear of old age, disease or death. Apparently a devotee may grow old, but he is not subjected to the symptoms of defeat experienced by a common man in old age. Consequently, old age does not make a devotee fearful of death, as a common man is fearful of death. When jarā, or old age, takes shelter of a devotee, Kālakanyā diminishes the devotee’s fear. A devotee knows that after death he is going back home, back to Godhead; therefore he has no fear of death. Thus instead of depressing a devotee, advanced age helps him become fearless and thus happy.

Srila Prabhupada's purport to 4.27.28
After much consideration, the King of the Yavanas decided to make the best use of a bad bargain. Kālakanyā was a bad bargain, and no one liked her, but everything can be used for the service of the Lord. Thus the King of the Yavanas tried to utilize her for some purpose. The purpose has already been explained — that is, Kālakanyā asjarā, the invalidity of old age, can be used to arouse a sense of fear in people so that they will prepare for the next life by engaging in Kṛṣṇa consciousness.


Foolish people accept unhappiness as happiness; therefore the King of the Yavanas decided to attack such foolish people imperceptibly by old age, disease, and ultimately death. Of course, after death there must be birth; therefore Yavana-rāja thought it wise to kill all the karmīs through the agency of Kālakanyā and thus try to make them aware that materialistic advancement is not actually advancement. Every living entity is a spiritual being, and consequently without spiritual advancement the human form of life is ruined.

Srila Prabhupada's purport to 4.27.30

Yavana-rāja’s brother was Prajvāra, and Kālakanyā was invalidity itself. Combined and strengthened by the soldiers of Yavana-rāja — namely nonhygienic conditions, illicit sex and ultimately a high degree of temperature to bring on death — they would be able to smash the materialistic way of life. In this connection it is significant that Nārada was immune to the attack of jarā, or invalidity. Similarly jarā,or the destructive force, cannot attack any follower of Nārada Muni or another pure Vaiṣṇava.

Srila Prabhupada's purport to 4.28.2
According to the Vedic system, before coming to such a stage one should leave home and take sannyāsa to preach the message of God for the duration of life. However, if one sits at home and is served by his beloved wife and children, he certainly becomes weaker and weaker due to sense gratification. When death finally comes, one leaves the body devoid of spiritual assets.

The Lord's Causeless Mercy Gives One the Ability to Render Service - Part 1

Dhruva Maharaja patiently executed his spiritual master Narada Muni's instruction, by doing so he attained the Supreme Perfection of life which was to receive darshan of the Lord. When the Lord was standing before him, he was speechless and stunned. He was unable to offer prayers in glorification of the Lord. The Lord very mercifully blessed him by touching His conchshell on his head.

He was thus enabled by the causeless mercy of the Lord , to offer fitting prayers.

• The Lord's mercy is needed to render service:
• Srila Prabhupada states in the purport to the verse 4.9.5:"To glorify or offer prayers unto the Supreme, one needs the Lord’s mercy. One cannot write to glorify the Lord unless one is endowed with His causeless mercy."
• Dhruva Maharaja experiences difference in himself:
• Therefore when Dhruva Mahārāja found this difference within himself, he could immediately understand that it was because of the causeless mercy of the Lord. 
• Acknowledgement and Gratitude for the mercy received
• He offered obeisances to the Lord with great respect and reverence, completely understanding that the Lord’s favor was upon him. 

How does such spiritual enlivenment work?

From Srila Prabhupada's purport to SB 4.9.6

• Action of the internal potency
• This spiritual enlivenment of Dhruva Mahārāja’s senses and mind was due to the action of the internal potency of the Lord.
• Connect with internal potency through chanting:
• Spiritual enlightenment is possible by the mercy of the spiritual energy of the Lord. The chanting of the Hare Kṛṣṇa mantra is first addressed to the spiritual energy of the Lord, Hare.
• When does the spiritual energy act:
•  This spiritual energy acts when a living entity fully surrenders and accepts his position as an eternal servitor. 
• When a person places himself at the disposal or order of the Supreme Lord, that is called sevonmukha; at that time the spiritual energy gradually reveals the Lord to him.
• Nothing is possible without the revelation by the spiritual energy
• Without revelation by the spiritual energy, one is unable to offer prayers glorifying the Lord.
•  Any amount of philosophical speculation or poetic expression by mundane persons is still considered to be the action and reaction of the material energy. 
• Action  of the spiritual energy:
• When one is actually enlivened by the spiritual energy, all his senses become purified, and he engages only in the service of the Lord. At that time his hands, legs, ears, tongue, mind, genitals — everything — engage in the service of the Lord. 
• Such an enlightened devotee no longer has any material activities, nor has he any interest in being materially engaged. This process of purifying the senses and engaging them in the service of the Lord is known as bhakti, or devotional service.
• "Mechanically Engaged" followed by "Engagement with spiritual understanding":
•  In the beginning, the senses are engaged by the direction of the spiritual master and śāstra, and after realization, when the same senses are purified, the engagement continues.
•  The difference is that in the beginning the senses are engaged in a mechanical way, but after realization they are engaged in spiritual understanding.

Further continued in 

The Lord's Causeless Mercy Gives One the Ability to Render Service - Part 2

The Lord's Darshan makes one aloof from sex attraction and one desires to see nothing else but the Lord

From the purport to SB 3.28.32:

A yogī should similarly meditate on the most benevolent smile of Lord Śrī Hari, a smile which, for all those who bow to Him, dries away the ocean of tears caused by intense grief. The yogī should also meditate on the Lord’s arched eyebrows, which are manifested by His internal potency in order to charm the sex-god for the good of the sages.

Purport:

It is stated in this verse that the charming eyebrows of the Lord are so fascinating that they cause one to forget the charms of sense attraction. The conditioned souls are shackled to material existence because they are captivated by the charms of sense gratification, especially sex life. The sex-god is called Makara-dhvaja. The charming brows of the Supreme Personality of Godhead protect the sages and devotees from being charmed by material lust and sex attraction. Yāmunācārya, a great ācārya, said that ever since he had seen the charming pastimes of the Lord, the charms of sex life had become abominable for him, and the mere thought of sex enjoyment would cause him to spit and turn his face. Thus if anyone wants to be aloof from sex attraction, he must see the charming smile and fascinating eyebrows of the Supreme Personality of Godhead.

3.28.33
With devotion steeped in love and affection, the yogī should meditate within the core of his heart upon the laughter of Lord Viṣṇu. The laughter of Viṣṇu is so captivating that it can be easily meditated upon. When the Supreme Lord is laughing, one can see His small teeth, which resemble jasmine buds rendered rosy by the splendor of His lips. Once devoting his mind to this, the yogī should no longer desire to see anything else.

Purport:
If the yogī is able to place the beautiful face of the Lord in the core of his heart, he will be completely satisfied. In other words, when one is absorbed in seeing the beauty of the Lord within himself, the material attraction can no longer disturb him.

Residual Sense Enjoyment propensities are burned by Devotional Service - Uddhava Gita

SB 11.20.27-28: Having awakened faith in the narrations of My glories, being disgusted with all material activities, knowing that all sense gratification leads to misery, but still being unable to renounce all sense enjoyment, My devotee should remain happy and worship Me with great faith and conviction. Even though he is sometimes engaged in sense enjoyment, My devotee knows that all sense gratification leads to a miserable result, and he sincerely repents such activities.

SB 11.20.29: When an intelligent person engages constantly in worshiping Me through loving devotional service as described by Me, his heart becomes firmly situated in Me. Thus all material desires within the heart are destroyed.

SB 11.20.30: The knot in the heart is pierced, all misgivings are cut to pieces and the chain of fruitive actions is terminated when I am seen as the Supreme Personality of Godhead.

SB 11.20.31: Therefore, for a devotee engaged in My loving service, with mind fixed on Me, the cultivation of knowledge and renunciation is generally not the means of achieving the highest perfection within this world.

Those fixed in devotion do not have material desires

SB 10.22.26: The desire of those who fix their minds on Me does not lead to material desire for sense gratification, just as barleycorns burned by the sun and then cooked can no longer grow into new sprouts.

The words mayy āveśita-dhiyām are very significant here. Unless one has achieved an advanced degree of devotion, one cannot fix the mind and intelligence on Kṛṣṇa, since Kṛṣṇa is pure spiritual existence. Self-realization is a state not of desirelessness but rather of purified desire, wherein one desires only the pleasure of Lord Kṛṣṇa. The gopīs were certainly attracted to Kṛṣṇa in a mood of conjugal love, and yet, having fixed their minds and indeed their entire existence completely on Kṛṣṇa, their conjugal desire could never manifest as material lust; rather, it became the most exalted form of love of Godhead ever seen within the universe.

Spiritual master helps us regain our spiritual identity

SB 7.15.43-44: In the conditioned stage, one's conceptions of life are sometimes polluted by passion and ignorance, which are exhibited by attachment, hostility, greed, lamentation, illusion, fear, madness, false prestige, insults, fault-finding, deception, envy, intolerance, passion, bewilderment, hunger and sleep. All of these are enemies. Sometimes one's conceptions are also polluted by goodness.
SB 7.15.45: As long as one has to accept a material body, with its different parts and paraphernalia, which are not fully under one's control, one must have the lotus feet of his superiors, namely his spiritual master and the spiritual master's predecessors. By their mercy, one can sharpen the sword of knowledge, and with the power of the Supreme Personality of Godhead's mercy one must then conquer the enemies mentioned above. In this way, the devotee should be able to merge into his own transcendental bliss, and then he may give up his body and resume his spiritual identity.
SB 7.15.46: Otherwise, if one does not take shelter of Acyuta and Baladeva, then the senses, acting as the horses, and the intelligence, acting as the driver, both being prone to material contamination, inattentively bring the body, which acts as the chariot, to the path of sense gratification. When one is thus attracted again by the rogues of viṣaya — eating, sleeping and mating — the horses and chariot driver are thrown into the blinding dark well of material existence, and one is again put into a dangerous and extremely fearful situation of repeated birth and death