Sexual Addiction reduces life span, intelligence, opulence and personal beauty

Srila Prabhupada's Purport to 4.27.21

The great sage Nārada Muni was a naiṣṭhika-brahmacārī — that is, he never had sex life. He was consequently an ever-green youth. Old age, jarā, could not attack him. The invalidity of old age can overcome an ordinary man, but Nārada Muni was different. Taking Nārada Muni to be an ordinary man, the daughter of Time confronted him with her lusty desire. It requires great strength to resist a woman’s attraction. It is difficult for old men, and what to speak of young. Those who live as brahmacārīs must follow in the footsteps of the great sage Nārada Muni, who never accepted the proposals of Jarā. Those who are too much sexually addicted become victims of jarā, and very soon their life span is shortened. Without utilizing the human form of life for Kṛṣṇa consciousness, the victims ofjarā die very soon in this world.

Srila Prabhupada's purport to 4.28.1

When a man is young, he does not care for old age but enjoys sex to the best of his satisfaction, not knowing that at the end of life his sexual indulgence will bring on various diseases, which so much disturb the body that one will pray for immediate death. The more one enjoys sex during youth, the more he suffers in old age.

SB 4.28.6: 

When King Purañjana was embraced by Kālakanyā, he gradually lost all his beauty. Having been too much addicted to sex, he became very poor in intelligence and lost all his opulence. Being bereft of all possessions, he was conquered forcibly by the Gandharvas and the Yavanas.

Purport: 

When a person is attacked by the invalidity of old age and is still addicted to sense gratification, he gradually loses all his personal beauty, intelligence and good possessions. He thus cannot resist the forceful attack of the daughter of Time.

Working hard for little happiness

From the purport to SB 4.25.4

Nārada Muni asked King Prācīnabarhiṣat: My dear King, what do you desire to achieve by performing these fruitive activities? The chief aim of life is to get rid of all miseries and enjoy happiness, but these two things cannot be realized by fruitive activity.

In this material world there is a great illusion which covers real intelligence. A man in the mode of passion wants to work very hard to derive some benefit, but he does not know that time will never allow him to enjoy anything permanently. Compared with the work one expends, the gain is not so profitable. Even if it is profitable, it is not without its distresses. If a man is not born rich and he wants to purchase a house, cars and other material things, he has to work hard day and night for many years in order to possess them. Thus happiness is not attained without undergoing some distress.

Actually, pure happiness cannot be had within this material world. If we wish to enjoy something, we must suffer for something else. On the whole, suffering is the nature of this material world, and whatever enjoyment we are trying to achieve is simply illusion. After all, we have to suffer the miseries of birth, old age, disease and death. We may discover many fine medicines, but it is not possible to stop the sufferings of disease or death. Actually, medicine is not the counteracting agent for either disease or death. On the whole there is no happiness in this material world, but an illusioned person works very hard for so-called happiness. Indeed, this process of working hard is actually taken for happiness. This is called illusion.