To summarize this brahmacarya life in this age, we have given a simple formula, that "No illicit sex." Sex is there. Sex is not bad. In the Bhagavad-gītā it is said, dharmāviruddhaḥ kāmo 'smi (BG 7.11): "Sex life which is not against the religious principles of life, that is I am." Kṛṣṇa says.
So dharmāviruddha, according to Vedic civilization, one should have sex indulgence only once in a month. That is the prescription. And when the wife is pregnant there is no sex life. That is dharmāviruddha. That is not against the religious principles. Even in your life, married life, if you indulge sex life more than once in a month, or in pregnancy, that is against religious principle.
So Kṛṣṇa says, dharmāviruddhaḥ kāmo 'smi: "Lust, sex indulgence, which is not against the rules of religious principles, that is I am." That means only for begetting children, nice children, so that there may not be disturbance. Unless there are nice population, children, born in a systematic way, how you can expect peace in the world? That is described in the Bhagavad-gītā: when there are varṇa-saṅkara the whole world becomes hell. This is described in the Bhagavad-gītā.
So the life of austerity begins from the life of celibacy, brahmacarya. So brahmacarya, the descriptions are given here, how you can execute brahmacārī life. You cannot think of sex life, you cannot talk of sex life, you cannot whisper about sex life. There are eight types of different regulation to stop sex life. But these things are very difficult in this age. Therefore we have simply summarized that don't have sex life beyond the married life. That is not good.
Then how brahmacarya can be executed? That is also given here: tapasā brahmacaryeṇa śamena (SB 6.1.13). Śamena means controlling the mind. The yoga system, aṣṭāṅga-yoga system, practicing the āsana, sitting posture, breathing exercise, controlling the senses from outside engagement, pratyāhāra, these are . . . this yoga system is meant for controlling the mind and controlling the sense. If there is no control of mind and no control of senses, the so-called yoga practice is bogus. It has no meaning. Yoga indriya saṁyama. Yoga means to control the senses. That is the real meaning of yoga.
So if one is unable to control the senses . . . I have seen in some yoga practice institution in New York, they are practicing some . . . this āsana, and just after finishing, immediately smoking. You see? This much control they learned. So these, these are all bogus. This is not yoga system. Yoga system is not so easy, especially in this age. Yoga system means to control the senses, control the mind; and control the mind means you have to control so many things—your eating, your sleeping, your behaving. These are prescribed in the Bhagavad-gītā, how to practice the aṣṭāṅga-yoga.
You have to find out a suitable place, a sacred place, a solitary place. Therefore real yogīs, they used to go to Himalaya. Sometimes some young men here, in your country, they inquire from me how to go to Himalaya. And what you'll do there, going there, Himalaya? So you are not practiced. So instead of practicing yoga in the Himalaya, you practice yoga here. We have come here to help you. Here this Kṛṣṇa consciousness movement is there. If you are serious about practicing yoga, this . . . take bhakti-yoga. That will come, how it happens in the next few lines.