Yoga is acheived through the development and perfection of discrimination: the knowledge that reveals what is real and what is not. 

"The afflictions are avidya [ignorance], egoism, attachment, hatred, and clinging to life. Avidya [ignorance] is the field of those (afflictions) that follow, whether they be in a dormant, thinned out, overpowered or expanded condition. Avidya [ignorance] is taking the non-eternal, impure, painful, and not-self as the eternal, pure, happy Self. The method for the removal of ignorance is the continuous practice of vivekakhyati." —Patanjali, Yoga Sutras

"The knowers [who] behold Reality will teach you knowledge—having known which, you will not again succumb to confusion… Even if one is the most sinful of all sinners, one shall yet cross over the ocean of sin by the raft of Self-knowledge alone. As the blazing fire reduces wood to ashes; similarly, the fire of Self-knowledge reduces all bonds of karma to ashes...” —Krishna, Bhagavad-gita

“Bliss is the essential nature of man… Man’s essential nature is divine, the awareness of which he has lost because of his animal propensities and the veil of ignorance.” —Swami Sivananda