In the first chapter of the Yoga Sutras, Patanjali answers the question: What is Yoga? with a description of the result gained through the practice of deep mediation:
The ancient philosophy of yoga tells us yes; there is an eternal, ever-present reality within us that transcends the limits that society imposes on us.
Yoga is a portable art form, free from costly equipment and supplies. All it requires is a sense of adventure and a willingness to explore the vastness of the Self.
In the practices of yoga our resistance to the natural state o bliss and our attachment to the world of forms and senses is made apparent. When we feel limitation in the body or the mind, it is an opportunity to concentrate on our true nature, which is love itself, beyond limitation.
When you stop identifying with your thoughts, the fluctuations of mind, then there is Yoga, which is identification with the true Self; samadhi, happiness, bliss, and ecstasy. The Sanskrit term for meditation is dhyana.
Once we can sit down and draw inward without being distracted, we are prepared for meditation, which may happen spontaneously and naturally if the ability to concentrate the mind on one object and hold it there for some time has been mastered. We cannot make ourselves meditate. We can only make ourselves concentrate.
Sit down! Just sit down and hold still! Sounds simple, but it's not so easy when you have a mind filled with thoughts moving this way and that. The Sanskrit word asana is most commonly known as the name for the yogic practice of assuming various physical contortions, but it actually means "seat." By taking a seat, you establish a connection to the Earth. So asana, or the establishment of the seat, means the practice of connecting to the Earth. By Earth we mean all things, all manifestations of reality. Earth not only means the ground we walk on, the air we breathe, or the water we drink, but also all the beings-animals, plants, and minerals-that we come into contact with daily. Through asana practice we consciously connect to a touchable, tangible, sense-able level of reality.
According to Patanjali, the seat that you establish should be steady and joyful, in body as well as mind. The word asana, therefore, also describes the goal of this yoga practice, which is to consciously relate to all beings with steadiness and joy
Yogash chitta-vritti-nirodhah. (YS I:2)
Yoga is the cessation of the fluctuations, or whirlings, of the mind.
The benefits of asana practice, however, reach far greater than skin, muscles and joints. More than other physical practices, asana practice directly affects the endocrine system, stimulating and balancing the glandular secretions. The long term positive effect that asana practice can have on the endocrine system only comes about when the practice is daily. A healthy endocrine system contributes to a healthier physical body and can even slow down the aging process. One's metabolism becomes balanced resulting in better digestion and assimilation of food. Compulsive eating is curbed. The immune system is strengthened and stabilized. One feels more energetic and at the same time calm. Stress reduction occurs naturally, as emotions become stabilized. One gains access to inner wells of creativity. But perhaps the most extraordinary effect is the expansion of consciousness that occurs from the stimulation of the master glands through asana, especially regular inversion practice. When consciousness or the "knowing principal" expands to include cosmic awareness then the individual begins to perceive him/herself not as a separate insignificant person but as a dynamic player in the community life. Fear and insecurity begin to lift as true self confidence dawns. Eternal bliss or samadhi, the ultimate result of yoga practice, is realized. One feels their whole being-body and mind as a vehicle for the Divine Will.
Asana practice provides the means to purify our relationships with the world of others. Patanjali suggest that our relationships to others should be mutually beneficial and be based on steadiness and joy. (sthira-sukham asanam YS II.46) Our biological systems are made of the accumulation of all our past karmas. Every thought word or deed from every relationship from countless lives can be found in our body/mind personality self at this very moment. You can find it in the movement of the muscles, bones, joints, as well as how the blood flows and the lungs breathe and certainly in how the mind thinks and the heart feels.
As yogis we desire to move beyond the biological to the eternal; outside time and space, but to do that we must perfect that which is manifest within relative time and space. We need the help of the Divine Mother, Mother Nature. We are born into Nature it is our means for movement and change. Through Her blessing, we evolve. She gives us our unfolding life as a means for spiritual realization. As preparation for birth takes place in pregnancy, so preparation for the spiritual or non-biological state must be made while alive in physical manifestation. We can only move into the transcendental by going through that which is flesh and blood and seems actual. Through the experiences of life the soul evolves and becomes purified. When the soul through purification arrives in a state of sattvic balance then the self may begin to gain perception of the absolute Self.