Srila Prabhupada on Brahmacharya

So the tapasya life begins from celibacy, brahmacaryena. Sukadeva Gosvami recommends. Brahmacarya is described in the sastras that:
smaranam krrtanaṁ kelih prekṣanam guhyam asanam [sankalpo adhyavasaya].
1. smaraṇam [remembering], thinking of sex life, that is against brahmacarya. Complete celibacy means one should not think of even sex life.
2. kirtanam [chanting], talk of sex life. Our modern literature, newspaper and everything, simply full with talks of sex life. But this is against brahmacarya life.
3. kelih [performing], actually indulging in sex life.
4. Prekṣanam [looking], overlooking a nice boy or nice girl. That is also against brahmacarya. Read more...

5. guhyam [confidential], whispering between girls and boys. That is also against brahmacari.
6. asanam [sitting], “One should not allow oneself to sit on the same seat even with one’s own mother, sister or daughter, for the senses are so strong that even though one is very advanced in knowledge, he may be attracted by sex.” (Śrīmad-Bhāgavatam 9.19.16)
7. sankalpo [determination], determination of sex life.
8. adhyavasaya [endeavoring], endeavoring how to effect sex life.

So when we can stop all these activities, that is real brahmacarya. It is very difficult at the present age. Etān maithunyam aṣṭāṅgam pravadanti manīṣiṇaḥ vikārita brahmacaryaṁ eda astanam lakṣaṇaṁ iti(?). So brahmacarya means that you cannot think of sex life, you cannot talk of sex life, you cannot whisper about sex life, or you cannot endeavor for sex life. These eight types of activities in sex indulgence are against brahmacary life. But here it is prescribed that if you want to make solution of the problems of life, then you adopt, you have to adopt a life of tapasya, austerity, which begins from brahmacārī.

Srimad Bhagavatam 6.1.13-14

tapasa brahmacaryena

samena ca damena ca

tyagena satya-saucabhyam

yamena niyamena va

deha-vag-buddhijam dhira

dharmajnah sraddhayanvitah

ksipanty agham mahad api

venu-gulmam ivanalah

TRANSLATION

To concentrate the mind, one must observe a life of celibacy and not fall down. One must undergo the austerity of voluntarily giving up sense enjoyment. One must then control the mind and senses, give charity, be truthful, clean and nonviolent, follow the regulative principles and regularly chant the holy name of the Lord. Thus a sober and faithful person who knows the religious principles is temporarily purified of all sins performed with his body, words and mind. These sins are like the dried leaves of creepers beneath a bamboo tree, which may be burned by fire although their roots remain to grow again at the first opportunity.

PURPORT

Tapah is explained in the smrti-sastra as follows: manasas cendriyanam ca aikagryam paramam tapah. "Complete control of the mind and senses and their complete concentration on one kind of activity is called tapah." Our Krsna consciousness movement is teaching people how to concentrate the mind on devotional service. This is first-class tapah. Brahmacarya, the life of celibacy, has eight aspects: one should not think of women, speak about sex life, dally with women, look lustfully at women, talk intimately with women or decide to engage in sexual intercourse, nor should one endeavor for sex life or engage in sex life. One should not even think of women or look at them, to say nothing of talking with them. This is called first-class brahmacarya. If a brahmacari orsannyasi talks with a woman in a secluded place, naturally there will be a possibility of sex life without anyone's knowledge. Therefore a complete brahmacaripractices just the opposite. If one is a perfect brahmacari, he can very easily control the mind and senses, give charity, speak truthfully and so forth. To begin, however, one must control the tongue and the process of eating.

In the bhakti-marga, the path of devotional service, one must strictly follow the regulative principles by first controlling the tongue (sevonmukhe hijihvadau svayam eva sphuraty adah). The tongue (jihva) can be controlled if one chants the Hare Krsna maha-mantra, does not speak of any subjects other than those concerning Krsna and does not taste anything not offered to Krsna. If one can control the tongue in this way, brahmacarya and other purifying processes will automatically follow. It will be explained in the next verse that the path of devotional service is completely perfect and is therefore superior to the path of fruitive activities and the path of knowledge. Quoting from the Vedas, Srila Viraraghava Acarya explains that austerity involves observing fasts as fully as possible (tapasanasakena). Srila Rupa Gosvami has also advised that atyahara, too much eating, is an impediment to advancement in spiritual life. Also, in Bhagavad-gita (6.17) Krsna says:

yuktahara-viharasya

yukta-cestasya karmasu

yukta-svapnavabodhasya

yogo bhavati duhkha-ha

"He who is temperate in his habits of eating, sleeping, working and recreation can mitigate all material pains by practicing the yoga system."

In text 14 the word dhirah, meaning "those who are undisturbed under all circumstances," is very significant. Krsna tells Arjuna in Bhagavad-gita (2.14):

matra-sparsas tu kaunteya

sitosna-sukha-duhkha-dah

agamapayino 'nityas

tams titiksasva bharata

"O son of Kunti, the nonpermanent appearance of happiness and distress, and their disappearance in due course, are like the appearance and disappearance of winter and summer seasons. They arise from sense perception, O scion of Bharata, and one must learn to tolerate them without being disturbed." In material life there are many disturbances (adhyatmika, adhidaivika and adhibhautika). One who has learned to tolerate these disturbances under all circumstances is called dhira.