The First Necessity Is to Develop a Foundation for Spiritual Energy to Manifest :

Hatha Yoga begins with Asana, the “seat”, which provides the foundational basis for the further practices which are intended to liberate, direct, control and receive ever-greater energy into the physical frame. It is a quite normal occurrence that people living the ordinary life of humanity find that every little event, every little action of others or of the world, every little provocation of the senses leads to a “spilling” of the energy of life, much of it through an unconscious nervous process of movements, distractions and general restlessness, but also a good deal of it through inability to hold energy and the pressure it creates in the body-vital-mind continuum.

This occurs not only on the physical level, but also especially on the vital, nervous level and even on the mental level. We can identify with how disturbed we can become when someone says something we do not like, or does something that interferes with what we were wanting or intending to do. For the scientist of Yoga, these all represent “leaks” of energy that can be cured, and the process of curing these leaks prepares the body to hold substantially more energy than before, thus preparing it for the descent of higher levels of conscious awareness and the higher energy these levels bring with them.

Sri Aurobindo observes: “It is the sign of a constant inability of the body to hold even the limited life-energy that enters into or is generated in it, and consequently of a general dissipation of this Pranic force with a quite subordinate element of ordered and well-economised activity.” The normal life in the world deals with this through a series of accommodations and balancing acts to keep things relatively at an even keel until of course the various parts of the instrument begin to break down. With the increase of mental activity, these imbalances tend to increase because the mind now makes its own demands and overrides the normal accommodations of the physical-vital being left to its own devices.

“Therefore the first necessity of a greater status or action is to get rid of this disordered restlessness, to still the activity and to regulate it. The Hathayogin has to bring about an abnormal poise of status and action of the body and the life-energy, abnormal not in the direction of greater disorder, but of superiority and self-mastery.”

Therefore, Hatha Yoga begins with the Asana, acquiring a firm control over the physical body and its movements, and developing the power of immobility as a sign of increasing control over the body and the ability to thereby open to more powerful forces that are brought about through the subsequent stages of the practice of Hatha Yoga.

Sri Aurobindo.