Prabhupada: So you must be very enthusiastic that "I shall preach the glories of the Lord to my best capacity." It is not that one has to become very learned scholar to become a preacher. Simply it requires enthusiasm:
"My Lord is so great, so kind, so beautiful, so wonderful. So I must speak something about my Lord."
This is the qualification, enthusiasm. You may not know Krsna very perfectly. It is not possible to know Krsna very perfectly. Krsna is unlimited. We cannot know Krsna cent per cent. That is not possible. But Krsna reveals as far as possible you can understand. So if we are sincere servant of Krsna, and if we serve patiently, then Krsna reveals. The example is given in this connection: Just like a girl is married. Generally, a girl wants a child. But if she wants a child immediately after marriage, that is not possible. She must wait. She must serve her husband nicely. Just like a faithful wife. Time will come she will become pregnant and she will have child. Just like the girl must know because she's married, because she has got a husband, that there must be a child. It is a fact. It may be little later. Similarly, when you have entered into devotional service, bhakti-yoga, bhakti-marga, your success is assured, provided you are enthusiastic and patient. Not that "Immediately I want a child," "Immediately I become fully Krsna consciousness and perfect." No. There may be so many imperfections, because we are in the imperfect atmosphere. But patiently if you go on executing your duties in devotional service as it is directed in the sastras and confirmed by the spiritual master, then rest assured that your success is guaranteed. This is the way. You must execute the duties.
>>> Ref: Srila Prabhupada's lecture on The Nectar of Devotion – October 20, 1972, Vrndavana
