When the mind becomes still, pure consciousness and pure energy unite and become one leading to knowledge of the Self.

Samatvam Yoga Uchyate (BG Ch2, Sl-48)
Yoga is the science of training the mind to remain even in pleasure and pain, gain or loss, defeat or victory, success or failure. The world is based on a law of duality. The dual forces will always be there in life. We have to learn not to get affected by them and be able to rise above them.

Yogah Karmasu Kaushalam (BG Ch2, Sl-50)
Yoga is the science of performing right action in accordance with the universal Law of Karma. Through such actions we free ourselves from the bondage of the law and the consequent revolving in the cycles of repeated births and deaths. It is the science of selfless activity without the notion of being a doer and without seeking the fruits of the activities.

Dukha Samyoga Viyogam Yoga Samjnitam (BG Ch6, Sl-23 )
Pain free state is yoga. When the mind is free of all pain producing factors, that pain free state of the mind is called yoga.

Characteristic of Human Life

All life is one connected whole
The whole universe is considered as one gigantic living Being. We are a small part of that Being. This idea is the foundation of all spiritual teachings. 'Do unto others as you want others do unto you'. 'Love thy neighbor as thyself'. These teachings are based on the above idea.

Life exists at three major levels

Physical
Modern science has today given us some understanding of the immensity of the physical universe. Billions of galaxies exists in this universe. Billions of stars exists in each of these galaxies, most of these stars have their planetary systems. Life in some form, not necessarily like our own, exists in all these planets and stars.

Astral
Beyond the physical universe we have an astral universe made not of matter but of light and different densities of light energies. The astral universe is exquisitely more beautiful,and vaster than the physical universe. Higher life forms exists in the astral planets, stars and the astral universe.

Causal
Beyond the astral universe, there is a causal universe made of thoughts and ideas. This is once again vaster and more beautiful than the astral universe. The highest beings and the highest life forms exists in these causal planets, stars and the universe.