Devotional Service is just like a seed sown in the heart of a living entity and if he goes on hearing & chanting, that seed fructifies, just as the seed of a tree fructifies with regular watering. Thus the spirtitual plant of devotional Service grows gradually.
Devotional service is not a job, it is a privilege.
Speculative knowledge alone, without devotional service, is not able to give liberation. On the other hand, even without knowldege one can obtain liberation if one engages in the Lord's devotional service. — Sri Chaitanya Caritamrita, Madhya Lila, 22.21.
One can understand the Supreme Personality as He is only by devotional service and when he is in full consciousness of the Supreme Lord by such devotion, he can enter into the kingdom of God. — Bhagavad Gita, 18.55.