Yoga: The three principles of practice

All Yoga proceeds in its method by three principles of practice; first, purification, that is to say, the removal of all aberrations, disorders, obstructions brought about by the mixed and irregular action of the energy of being in our physical, moral and mental system; secondly, concentration, that is to say, the bringing to its full intensity and the mastered and self-directed employment of that energy of being in us for a definite end; thirdly, liberation, that is to say, the release of our being from the narrow and painful knots of the individualised energy in a false and limited play, which at present are the law of our nature. The enjoyment of our liberated being which brings us into unity or union with the Supreme, is the consummation; it is that for which Yoga is done.

Ref: The Synthesis of Yoga