God, on being worshipped, bestows steadiness in devotion which leads to surrender. On the devotee surrendering, God shows His mercy by manifesting as the Guru. The Guru, otherwise God, guides the devotee, saying that God is in you and He is the Self. This leads to introversion of the mind and finally to realization.
When a person has realized, a universal life-current takes possession of him and he becomes an instrument in its hands. His own separate will is gone. This is the real Self-surrender. This is the highest kundalini (the divine cosmic energy), this is real bhakti (devotion), this is jnana (knowledge of the Self).
– Sri Ramana Maharshi
