Sri Chaitanya Mahaprabhu showed by his personal life the validity of the doctrines of devotion described in Srimad Bhagavata. Holding Achintya-Bheda-bheda or identity-in-difference to be the nature of the Ultimate Reality whom he called Sri Krishna, Chaitanya demonstrated how Bhakti is the sure way to higher spiritual development.
Those who work at a thing heart and soul not only achieve success in it but through their absorption in that they also realize the supreme truth -- Brahman. Those who work at a thing with their whole heart receive help from God.
-Swami Vivekananda