Prabhupada Class on Bhakti Yoga: Bhagavad-gita 7.1 -- Ahmedabad Dec 13, 1972

Srila Prabhupada explains from Bhagavad-gita As It Is that the first class yogi is one who is always thinking of Krishna and goes on to elaborate how one benefits by simply understanding Krishna. If you simply understand Krishna then you know everything. Krishna is the root of everything.