To attain the mercy of the Lord, we have to feel ourselves to be very low, fallen, and unqualified, but at the same time, very eager to receive the mercy of the Lord. Therefore, even though we may chant improperly, if we chant with the motivation to please the Lord, the Lord accepts that just as much as someone who chants perfectly.
Caitanya Caritamrita Lectures Book, Madhya Lila: 1.195-218, Kiev-June12, 2000, Pg 209-210