[The following is from the book Ananda Yoga for Higher Awareness by Swami Kriyananda.]

The Purpose of Yoga Postures

In the main stream of life two currents, especially, may be observed. One is toward an expansion of awareness. The other is a sinking back into sleep and unawareness, a shutting out of reality, a longing for death. Positive and negative—in all of us, both of these trends may be observed.

To the extent that we draw the world to us, by an attitude of willingness, appreciation, kindness, joy, we express the positive current. When, by unwillingness, a critical attitude, selfishness, unkindness, grief, we push the world away from us, excluding it from our circle of awareness, we express the negative current. Man, unlike the lower animals, has the freedom greatly to quicken his evolutional climb toward perfect awareness—or, if he prefers, to fall back into the mires of unknowing from which he emerged. It is for him to rejoice in his existence, or merely to wallow in it.

Every growth in awareness is, in the last analysis, a growth in Self-awareness. What we observe in the world depends on our own capacity for observation. An anguished spirit will find in everything justification for its anguish. A joyous spirit will see reasons for gladness everywhere. No amount of pious maxims or lofty philosophy can bring light into man’s world beyond what already exists in his own consciousness.

The true purpose of yoga is to facilitate the development of this Self-awareness—not as a self-enclosure, but as a doorway to an expanded awareness of the surrounding universe, of truth, of very life.

Usually, hatha yoga (the science of yoga asanas, or postures) is taught only from a standpoint of its benefits to the body...but much more is involved.

For by the yoga postures one can improve his mental outlook. He can achieve a richer, more harmonious emotional life. The postures are a definite aid to spiritual development. Particularly, from a standpoint of the approach of this book, they help one to develop a more vital awareness. The hatha yogi (a yogi is one who practices the yoga science) learns to include his body in the general circle of his awareness, to live in his body instead of merely existing in it. By increasing his physical awareness he can free his mind from the imperatives to commonly imposed upon man by his body: weakness, fatigue, physical sluggishness and resistance, discomfort, pain. He is thus able to make the body the servant of his will. Health, as it is usually conceived, is negative: a mere absence of disease. But the yoga postures help to create a joyous sense of vitality and well-being. They make the body an ally, not a neutral neighbor or even a foe, of the soul in its search for expanding awareness.

Physical Postures and Mental Awareness

Certain bodily postures are naturally associated with certain mental attitudes. When the mind is discouraged, the body tends to stoop forward. Courage tends to make the body erect. Under the influence of aggressive feelings, the shoulders often become hunched upward, the fists become clenched. When feeling stubborn a person may jut his jaw forward. When he is inspired, his eyes will look upward; when depressed, they will look downward. Poise, or lack of it, is reflected in the way one sits, in the way he stands, in the movement of his hands.

Even the pattern of breathing is affected by one’s mental attitudes. Fear and anxiety tighten the stomach muscles. A person with a narrow, self-restrictive outlook inclines to draw in the sides of his rib cage. One who suppresses his natural feelings tends to hold in the upper part of his chest. Can a person with all of these psychological problems find any room for breathing at all? Hardly! The amount of oxygen he permits his system amounts to starvation wages, truly.

But just as one’s mental attitudes affect his body, so also his bodily postures affect his mind. Slumped shoulders and a bent spine can actually, to some extent, induce moodiness. Tensed stomach muscles can—again, to some extent—induce mental anxiety. This simple fact, obvious enough to anyone, is turned by yogis into a major key to the problem of self-development.

For, as physical tensions can induce, as well as reinforce, mental tensions, so physical relaxation can bring serenity to a worried mind. Ripples, after striking the shore of a pond, return toward their source. An effect, in its turn, is often found to affect its initial cause. If this first effect can be altered, the cause may be substantially altered also.

It is difficult to change one’s mental outlooks. It is difficult even to view them objectively. The thoughts with which one would disperse his delusions are already poisoned by the very delusions he is trying to disperse!

To change oneself physically, however, in such a way as to influence the mind to adopt a similarly reformed outlook is a relatively simple undertaking. Harmonize the body, and it will be easier to harmonize the mind. This principle is fundamental to the science of hatha yoga. And it applies, in varying degrees of subtlety, to all levels of yoga teaching.

The breathing, for example, is affected by one’s state of mind. Change the breathing, and one’s mental state may be changed, too.

“But,” you may ask, “how, specifically, can a bodily posture or a breathing exercise affect one’s mental outlook?”

The connection between the body and the mind is the energy (prana) in the body. It is energy that transmits signals from the sense to the brain. It is energy that carries impulses from the brain to the body. When the flow of this energy is obstructed or set out of balance, there is a corresponding inharmony in both body and mind. The yoga postures are designed to promote and to harmonize the flow of energy in the body. The perceptive hath yogi, understanding this truth, will endeavor to become conscious of his energy, and will use the postures and breathing exercises as a means primarily to developing this awareness. For awareness is the first and most important stage towards gaining control.

One of the most fascinating discoveries that the practicing yogi makes concerning his own psycho-physical natures is that the positive and negative currents, which we discussed earlier, have their literal counterpart in a directional flow of the energy in his body. When he thinks positively, there is an upward flow, literally, of this energy. When he thinks negatively, there is a downward flow. It is no accident that common parlance speaks of feeling “uplifted,” “on top of the world,” of feelings though one’s soul were “flying,” when one feels happy. Nor is it accidental that one speaks of feeling “downcast,” “under the weather,” “dragged down,” “depressed,” when he feels sad.

Yogis say that, in an uplifted state of awareness, the energy is literally concentrated in the upper part of the body. At such times, the very eyes tend to look upward, the corners of the mouth to turn up; everything about the body suggest an upliftment of this inner energy. But in a depressed state of mind, the energy becomes concentrated in the lower part of one’s body: The eyes become downcast; the corners of the mouth turn downward; there is a sagging in the face, in the shoulders, in the arms; one’s whole body suggests a sense of heaviness, of being earthbound.

It does not seem likely that heaven and hell are above us or below us in an objective sense, as tradition claims. But it is not difficult to demonstrate to oneself that heaven is up, and hell down, from a standpoint of one’s own inner awareness.

An all-important purpose of the yoga postures, and indeed of all yoga practices, is to assist the direction of this inner energy toward the upper part of the body, especially toward the brain. Just as a calm, relaxed pose can help to induce a calm state of mind, even so, the simple process of changing the inner level of one’s energy can have a tremendous effect on the quality of his awareness. By directing his energy upward, it becomes relatively easy for him to develop a positive mental outlook—to become kind, willing, energetic, and joyous.

For our virtues and vices are not really we, ourselves. They are reflections, only, of the plane of consciousness on which we live. As that plane changes, the traits of our personality change also.

Lest it be imagined that virtue can be developed by mechanics alone, it must be stressed that without an endeavor also to change the quality of one’s thoughts, no deep-seated good can be achieved. Our thoughts are the prime cause of whatever harmony or inharmony we experience, not in the mind only, but in the body as well. To concentrate on soothing the effects while continuing to aggravate the initial cause would be like trying to placate a cat with milk while continuing to stand on its tail.

But if there is a sincere desire to improve one’s state of mental awareness, then the yoga postures, the breathing exercises, and above all, the deliberate effort to harmonize and uplift one’s inner energy, can be a tremendous aid to this worthwhile endeavor.