For an ordinary, materialistic person who is conditioned by the modes of the material nature, it is very difficult for him to understand what devotion is. A person cannot taste honey by licking the exterior surface of the bottle. To understand the sweet taste of the honey, one has to open the bottle and taste its contents.Thus if one wants to understand the nature of devotional service, he has to come in contact with the devotee of the Lord. We are most fortunate, because Sri Caitanya Mahäprabhu appears in this Age of Kali as the hidden avatära in the form of a devotee of the Lord to teach devotional service by practicing it Himself. Krsnadasa Kaviraja Gosvämi explains in Caitanya-caritamrta that Lord Sri Caitanya Mahaprabhu is an ocean of transcendental mercy. Although the subject matter of bhakti is very difficult to understand, Lord Caitanya has made this understanding very easily accessible for the fallen souls in this Age of Kali.
LFD Vol 3,Devotional Service Pg 155, last paragraph