Krishna : Those who have excessive attachment or aversion cannot become a devotee. 

Arjuna: How does anyone ever become a devotee. It seems to be impossible to become a devotee. 

Krishna: Those who are pious in the previous and in this life, by the mercy of pure devotees attain devotion to Me. The pure devotees wander all over the earth to give mercy to the fallen conditioned souls.

- HH.Purnachandra Goswami BG audio rendition chapter 7