Many ask me whether pranayama ... postpones old age. Why worry about it? Death is certain. Let it come when it comes. Just keep working. The soul has no age. It doesn't die. Only the body decays. And yet, we must never forget the body, since it is the garden we must cherish and cultivate.
B.K.S. IyengarWillpower is concrete, not ethereal. When you do something, you demonstrate your willpower, and it becomes all the easier to have the same power of will the next time.
B.K.S. IyengarTo do is hard, but to teach is still harder. Do not teach only to teach. Teach to improve the pupil. To be a teacher requires tremendous, vigorous discipline on oneself. We are teachers because somebody demands it from us. But the teacher should first rub his own self, and teach afterwards
B.K.S. Iyengar