Yoga strengthens the life force, making the body immune to psychological manipulations. With this psyche present in its own power one can take the path to enlightenment. My way of describing this is that you are Yang (postures, when you do them), until you are Yin (breath, during the day), until you are God (unconsciously, as per when you are asleep).

An able psyche has but one thing to do - realise the divine presence.