A great saint and a devotee Prahlada Maharaja points out the problems of sex life. The following sloka is from the ancient scripture Srimad Bhagavatam with the purport by His Divine Grace A.C.Bhaktivedanta Swami Prabhupada.
yan maithunadi-grhamedhi-sukham hi tuccham
kanduyanena karayor iva duhkha-duhkham
trpyanti neha krpana bahu-duhkha-bhajah
kandutivan manasijam visaheta dhirah
Sex life is compared to the rubbing of two hands to relieve an itch. Grhamedhis, so-called grhasthas who have no spiritual knowledge, think that this itching is the greatest platform of happiness, although actually it is a source of distress. The krpanas, the fools who are just the opposite of brahmanas, are not satisfied by repeated sensuous enjoyment. Those who are dhira, however, who are sober and who tolerate this itching, are not subjected to the sufferings of fools and rascals.
Materialists think that sexual indulgence is the greatest happiness in this material world, and therefore they make elaborate plans to satisfy their senses, especially the genitals. This is generally found everywhere, and specifically found in the Western world, where there are regular arrangements to satisfy sex life in different ways. Actually, however, this has not made anyone happy. Even the hippies, who have given up all the materialistic comforts of their fathers and grandfathers, cannot give up the sensational happiness of sex life. Such persons are described here as krpanas, misers. The human form of life is a great asset, for in this life one can fulfill the goal of existence. Unfortunately, however, because of a lack of education and culture, people are victimized by the false happiness of sex life. Prahlada Maharaja therefore advises one not to be misled by this civilization of sense gratification, and especially not by sex life. Rather, one should be sober, avoid sense gratification and be Krsna conscious. The lusty person, who is compared to a foolish miser, never gets happiness by sense gratification. The influence of material nature is very difficult to surpass, but as stated by Krsna in Bhagavad-gita (7.14), mam eva ye prapadyante, mayam etam taranti te: if one voluntarily submits to the lotus feet of Krsna, he can be saved very easily.
In reference to the low-grade happiness of sex life, Yamunacarya says in this connection:
yad-avadhi mama cetah krsna-padaravinde
nava-nava-rasa-dhamany udyatam rantum asit
tad-avadhi bata nari-sangame smaryamane
bhavati mukha-vikarah susthu nisthivanam ca
"Since I have been engaged in the transcendental loving service of Krsna, realizing ever-new pleasure in Him, whenever I think of sex pleasure, I spit at the thought, and my lips curl with distaste." Yamunacarya had formerly been a great king who enjoyed sexual happiness in various ways, but since he later engaged himself in the service of the Lord, he enjoyed spiritual bliss and hated to think of sex life. If sexual thoughts came to him, he would spit with disgust.