Captivation due to illicit sex( husband or wife)

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Systematic Grhastha Life as enjoined in the Vedas is better than irresponsible sinful life

From Srila Prabhupada's Purport to 4.26.26:

Both man and woman desire one another; that is the basic principle of material existence. Women in general always keep themselves beautiful so that they can be attractive to their lusty husbands. When a lusty husband comes before his wife, the wife takes advantage of his aggressive activities and enjoys life. Generally when a woman is attacked by a man — whether her husband or some other man — she enjoys the attack, being too lusty. In other words, when one’s intelligence is properly utilized, both the intellect and the intelligent person enjoy one another with great satisfaction. As stated in Śrīmad-Bhāgavatam (7.9.45):

yan maithunādi-gṛhamedhi-sukhaṁ hi tucchaṁ
 kaṇḍūyanena karayor iva duḥkha-duḥkham

The actual happiness of the karmīs is sex life. They work very hard outside the home, and to satiate themselves after their hard labor, they come home to enjoy sex life. King Purañjana went to the forest to hunt, and after his hard labor he returned home to enjoy sex life. If a man lives outside the home and spends a week in a city or somewhere else, at the end of the week he becomes very anxious to return home and enjoy sex with his wife. This is confirmed in Śrīmad-Bhāgavatam: yan maithunādi-gṛhamedhi-sukhaṁ hi tuccham. Karmīs work very hard simply to enjoy sex. Modern human society has improved the materialistic way of life simply by inducing unrestricted sex life in many different ways. This is most prominently visible in the Western world.

From 4.26.23:

An effeminate husband, simply being attracted by the external beauty of his wife, tries to become her most obedient servant. Śrīpāda Śaṅkarācārya has therefore advised that we not become attracted by a lump of flesh and blood. The story is told that at one time a man, very much attracted to a beautiful woman, wooed the woman in such a way that she devised a plan to show him the ingredients of her beauty. The woman made a date to see him, and before seeing him she took a purgative, and that whole day and night she simply passed stool, and she preserved that stool in a pot. The next night, when the man came to see her, she appeared very ugly and emaciated. When the man inquired from her about the woman with whom he had an engagement, she replied, “I am that very woman.” The man refused to believe her, not knowing that she had lost all her beauty due to the violent purgative that caused her to pass stool day and night. When the man began to argue with her, the woman said that she was not looking beautiful because she was separated from the ingredients of her beauty. When the man asked how she could be so separated, the woman said, “Come on, and I will show you.” She then showed him the pot filled with liquid stool and vomit. Thus the man became aware that a beautiful woman is simply a lump of matter composed of blood, stool, urine and similar other disgusting ingredients. This is the actual fact, but in a state of illusion, man becomes attracted by illusory beauty and becomes a victim of māyā.

From 4.25.62:

1. Just to satisfy his desires, the King got the Queen, and thus he became cheated by material existence. Although he was not willing to do so, he remained a pet animal under the control of material intelligence.
2.  Just as a pet monkey dances according to the desires of its master, the King danced according to the desires of the Queen. In Śrīmad-Bhāgavatam (5.5.2) it is said, mahat-sevāṁ dvāram āhur vimukteḥ: if one associates with a saintly person, a devotee, one’s path of liberation becomes clear.
3.  But if one associates with a woman or with a person who is too much addicted to a woman, his path of bondage becomes completely clear.
4. On the whole, for spiritual advancement one must give up the company of women. This is what is meant by the order of sannyāsa, the renounced order.
5. Before taking sannyāsa, or completely renouncing the material world, one has to practice avoiding illicit sex. Sex life, licit or illicit, is practically the same, but through illicit sex one becomes more and more captivated.
6. By regulating one’s sex life there is a chance that one may eventually be able to renounce sex or renounce the association of women. If this can be done, advancement in spiritual life comes very easily.

How one becomes captivated by the association of one’s dear wife is explained in this chapter by Nārada Muni.

1.  Attraction for one’s wife means attraction for the material qualities.
2. One who is attracted by the material quality of darkness is in the lowest stage of life, whereas one who is attracted by the material quality of goodness is in a better position. 
3. Sometimes we see that when a person is on the platform of material goodness, he is attracted more or less by the cultivation of knowledge.
4. This is, of course, a better position, for knowledge gives one the preference to accept devotional service. Unless one comes to the platform of knowledge, the brahma-bhūta stage, one cannot advance in devotional service.