The great saint Śaṅkarācārya has described the breasts of women, especially young women, as nothing but a combination of muscles and blood, so one should not be attracted by the illusory energy of raised breasts with nipples. They are agents of māyā meant to victimize the opposite sex. Because the breasts are equally attractive, they are described as sama-vṛttau. The sex impulse remains in an old man's heart also, even up to the point of death. To be rid of such agitation, one must be very much advanced in spiritual consciousness, like Yāmunācārya, who said:
yad-avadhi mama cetaḥ kṛṣṇa-pādāravinde
nava-nava-rasa-dhāmany udyataṁ rantum āsīt
tad-avadhi bata nārī-saṅgame smaryamāṇe
bhavati mukha-vikāraḥ suṣṭhu niṣṭhīvanaṁ ca
"Since I have been engaged in the transcendental loving service of Kṛṣṇa, realizing ever-new pleasure in Him, whenever I think of sex pleasure, I spit at the thought, and my lips curl with distaste."

(Srimad Bhagavatam---------4:25:24--------purport).

A living entity is never satisfied with a woman unless he is trained in the system of brahmacarya. Generally a man's tendency is to enjoy many women, and even at the very end of life the sex impulse is so strong that even though one is very old he still wants to enjoy the company of young girls. Thus because of the strong sex impulse the living entity becomes more and more involved in this material world.

(Srimad Bhagavatam---------4:25:44--------purport).

If one enjoys his senses unrestrictedly, he leads a sinful life. The animals do not violate the laws of nature. For example, the sex impulse in animals is very strong during certain months of the year. The lion is very powerful. He is a flesh-eater and is very strong, but he enjoys sex only once in a year. Similarly, according to religious injunctions a man is restricted to enjoy sex only once in a month, after the menstrual period of the wife, and if the wife is pregnant, he is not allowed sex life at all.
(Srimad Bhagavatam---------4:27:5--------purport).

Since the body is a great city, there must be various arrangements such as lakes and gardens for sense enjoyment. Of the various parts of the body, those which incite sexual impulses are referred to here indirectly. Because the body has genitals, when the living entity attains the right age—be he man or woman—he becomes agitated by the sex impulse. As long as one remains a child, he is not agitated by seeing a beautiful woman. Although the sense organs are present, unless the age is ripe there is no sex impulse. The favorable conditions surrounding the sex impulse are compared here to a garden or a nice solitary park. When one sees the opposite sex, naturally the sex impulse increases. It is said that if a man in a solitary place does not become agitated upon seeing a woman, he is to be considered a brahmacārī. But this practice is almost impossible. The sex impulse is so strong that even by seeing, touching or talking, coming into contact with, or even thinking of the opposite sex—even in so many subtle ways—one becomes sexually impelled. Consequently, a brahmacārī or sannyāsī is prohibited to associate with women, especially in a secret place. The śāstras enjoin that one should not even talk to a woman in a secret place, even if she happens to be one's own daughter, sister or mother. The sex impulse is so strong that even if one is very learned, he becomes agitated in such circumstances. If this is the case, how can a young man in a nice park remain calm and quiet after seeing a beautiful young woman?
(Srimad Bhagavatam---------4:25:17--------purport).

The body has already been compared to a beautiful garden. During youth the sex impulse is awakened, and the intelligence, according to one's imagination, is prone to contact the opposite sex. In youth a man or woman is in search of the opposite sex by intelligence or imagination, if not directly. The intelligence influences the mind, and the mind controls the ten senses. Five of these senses gather knowledge, and five work directly. Each sense has many desires to be fulfilled. This is the position of the body and the owner of the body, purañjana, who is within the body.
(Srimad Bhagavatam---------4:25:20--------purport).

When one begins to burn firewood, there is smoke and agitation in the beginning. Although there are so many disturbances in the beginning, once the fire is completely set, the firewood burns steadily. Similarly, when both husband and wife follow the regulative principles of austerity, they remain silent and are not agitated by sex impulses. At such a time both husband and wife are benefited spiritually. One can attain this stage of life by completely giving up a luxurious mode of life.
(Srimad Bhagavatam---------4:28:44--------purport).

Simply by engaging in the service of her exalted husband, who must be a pure devotee, the wife will never be agitated by sex impulses. The vānaprastha stage is exactly like this. Although the wife remains with the husband, she undergoes severe austerities and penances so that although both husband and wife live together, there is no question of sex. In this way both husband and wife can live together perpetually.
(Srimad Bhagavatam---------4:28:44--------purport).

Being a man, the husband is generally more advanced than his wife. Nonetheless, the wife is expected to give up all luxurious habits. She should not even dress nicely or comb her hair. Hair combing is one of the main businesses of women. In the vānaprastha stage the wife should not take care of her hair. Thus her hair will become tangled in knots. Consequently the wife will no longer be attractive to the husband, and she herself will no longer be agitated by sex impulses. In this way both husband and wife can advance in spiritual consciousness.
(Srimad Bhagavatam---------4:28:44--------purport).

In the Padma Purāṇa there is a statement of submission in feeling by devotees praying to the Lord: "My Lord, I know that young girls have natural affection for young boys, and that young boys have natural affection for young girls. I am praying at Your lotus feet that my mind may become attracted unto You in the same spontaneous way." The example is very appropriate. When a young boy or girl sees a member of the opposite sex there is a natural attraction, without the need for any introduction. Without any training there is a natural attraction due to the sex impulse. This is a material example, but the devotee is praying that he may develop a similar spontaneous attachment for the Supreme Lord, free from any desire for profit and without any other cause.
(Nectar of Devotion).

One should take prasāda at scheduled times and should not eat in restaurants or sweetmeat shops simply to satisfy the whims of the tongue or belly. If we stick to the principle of taking only prasāda, the urges of the belly and tongue can be controlled. In a similar manner, the urges of the genitals, the sex impulse, can be controlled when not used unnecessarily. The genitals should be used to beget a Kṛṣṇa conscious child, otherwise they should not be used. The Kṛṣṇa consciousness movement encourages marriage not for the satisfaction of the genitals but for the begetting of Kṛṣṇa conscious children.
(Nectar of Instruction).