Everything in moderation is the universal truth that accurately describes the goal behind the fourth yama Brahmacarya. I have heard specifics about to what specifically one should be applying the principles of moderation, but I don't personally find them individually important.
The key to this broad understanding of the fourth yama is as easy as it sounds.
In everything in your life—work, food, exercise, meditation, talking, shopping—practice moderation.
It's so simple right? We all know what is an appropriate amount of food for dinner, versus the heaping plate of pasta which so tempts us. That one's a no-brainer, because when we overdo it, we immediately feel the effects in the form of an upset stomach. When we over-indulge in exercise, our body becomes physically taxed. Et cetera. In Meditations From the Mat Rolf Gates describes this phenomenon well in his chapter on yamas. He says:
"There is the middle of the road and while on it we experience "knowledge, vigor, valor, and energy." If we indulge in immoderation, though, even for a moment, we immediately embark on another set of experiences-- namely, guilt, remorse, obsessive worry, inertia. It is really that simple." (p. 56)
I do consider this understanding of brahmacarya to be totally valid and not only that, completely comprehensible to everyone. But, I think there is more. I think that there are several layers of depth to the true brahmacarya.
I have heard another simple description of this yama, which explains it essentially as "conservation of one's individual essence." Which is like moderation from a different angle.
How to describe it?
- It is not giving too much of the self away, and equally not taking too much from others.
- It is understanding one's mind and the nature of the mind, and then acting accordingly.
- It is determining one's dharma, the overriding purpose of why we are here, and then pursuing it.
- It is practicing everything, and I mean everything from a place of love in one's heart.
How to practice it in everyday life?
Practice yoga! The true meaning behind the practice of yoga is self-realization. It all starts and ends with the self. Maybe the first years are mired in physically practice (asana) only, but that's okay! The important piece is that you are here on your mat, not running on the treadmill, and that there's a reason that you're consistently drawn back to the practice on the mat.
Furthermore, live out your days—your time at work, eating, sleeping, reading—practicing yoga. Practice the yamas and niyamas (I'll get there someday, I swear!) in all that you do. Set aside some time to meditate--even if it's just a few moments a month, begin to cultivate the notion of quieting your mind.
How to practice brahmacarya on the mat?
Practice with love. While we all want to have rockin' bods, there is no need to overdo your asana practice. Trust me, I'm as guilty of this as anyone. I love to push myself physically and am as competitive as the next guy. But we are not here practicing yoga in order to be bootylicious. We practice as part of a comprehensive plan to understand fully the Self.
And as with anything in life, your heart will tell you when you are practicing brahmacarya accurately. And when your essence is fully in balance you will know because you will shine.