The practice of yogasana for the sake of health, to keep fit, or to maintain flexibility is the external practice of yoga. While this is a legitimate place to begin, it is not the end. Even in simple asanas, one is experiencing the three levels of quest: the external quest, which brings firmness of the body; the internal quest, which brings steadiness of intelligence; and the innermost quest, which brings benevolence of spirit.
B.K.S. IyengarWhile doing the postures, your mind should be in half-consciousn ess, which does not mean sleep. It means silence, emptiness, space, which can then be filled with an acute awareness of the sensations given by the posture. You watch yourself from inside. It is a full silence.
B.K.S. IyengarPranayama teaches the aspirant to regulate his breathing and thereby control the mind.
B.K.S. IyengarAsanas maintain the strength and health of the body, without which little progress can be made. Asanas keep the body in harmony with nature
B.K.S. IyengarAs long as you do not feel the serenity in the body, in each and every joint, there is no chance for emancipation. You are in bondage. So while you are sweating and aching, let your heart be light and let it fill your body with gladness. You are not only becoming free, but you are also being free. What is not to be glad about? The pain is temporary. The freedom is permanent.
B.K.S. Iyengar