“The word ‘Yoga’ comes from a Sanskrit root ‘Yuj’ which means ‘to join’. In its spiritual sense, it is the process by which the identity of the individual soul and the Supreme Soul is realized by the Yogi. The human soul is brought into conscious communion with the Divine Reality. Just as camphor melts and becomes one with fire; just as a drop of water when it is thrown into the ocean, becomes one with the ocean; the individual soul, when it is purified, when it is freed from lust, greed, hatred and egoism, when it becomes pure (Sattvic), becomes one with the Supreme Soul.
Yoga is that state of Absolute Peace wherein there is neither imagination nor thought. Yoga is control of mind and its modifications. Yoga teaches us how to control the modifications of the mind and attain liberation. It teaches us how to transmute the unregenerate nature and attain the state of Divinity.
Equanimity is Yoga. Serenity is Yoga. Skill in actions is Yoga. Anything by which the best and the highest in life can be attained is also Yoga. Yoga is thus all-embracing, all-inclusive and universal in its application leading to all-round development of body, mind and soul.
Yoga brings in perfection, peace and lasting happiness. You can have calmness of mind at all times by the practice of Yoga. You can have restful sleep. You can have increased energy, vigour, vitality, longevity and a high standard of health. You can turn out efficient work within a short space of time. You can have success in every walk of life. Yoga will infuse in you new strength, confidence and self-reliance.
Yoga brings your emotions under control. It increases your power of concentration at work. Yoga discipline gives poise and tranquillity and miraculously rebuilds one’s life. The Yoga way of life deepens man’s understanding and enables him to know God and his relationship with Him.
Yoga leads from ignorance to wisdom, from weakness to strength, from disharmony to harmony, from hatred to love, from want to fullness, from limitation to infinitude, from diversity to unity, and from imperfection to perfection. Yoga gives hope to the sad and forlorn, strength to the weak, health to the sick and wisdom to the ignorant.
Through Yogic discipline, mind, body and the organ of speech work together harmoniously. For a Yoga practitioner, a new outlook, a new health, a new awareness and a new philosophy rush in and vividly transform his life.”
Swami Sivananda
http://www.dlshq.org/teachings/yoga.htm