With these thoughts in mind, the practitioner will understand that he has not "done" a posture once he has succeeded in assuming it. It is only at this point that he can begin truly to derive the benefits of that pose.
An important difference between these postures and calisthenics is that in yoga practice one must never strain. Relax, never force yourself, into the prescribed positions. Stretch only slightly, if at all, beyond the point of comfort. You will be astonished to see how many poses you can accomplish by progressively deeper relaxation.
Yogis illustrate their teaching of relaxation by the example of the cat. Observe this self-contained creature. It never uses more of its body at any given moment than it needs. Lift it up when it is resting, and observe how it hangs, limp, in your hands. Yet, so poised is it that, from a position of complete repose, it can leap to its feet in an instant, ready to defend itself against sudden danger.
The yogi, similarly, should act always from a center of poise and calmness, of mental and physical relaxation. When I first me the great yogi, Paramhansa Yogananda, he told me that, while sitting in a chair giving interviews, he was not even aware of his body below the chest. To be able so completely to relax the body when not using it, it is necessary first to be in full control of it; to be able at will to be fully conscious of every muscle.
The yoga postures, then, are not only a series of physical positions, but exercises in mental awareness. The yogi must be very deliberate in every movement. He must feel every muscle. Above all, he must try to become conscious of the energy as it directs the muscular movements. He must try to develop an awareness of his body as consisting primarily of energy.*