If we keep ourself on the material platform, then for thousand years we may chant, it will be difficult. That is called namaparadha. Of course, holy name is so powerful that even by chanting with offense, gradually he becomes pure. Therefore we should not give up chanting. Any circumstances, we should go on chanting Hare Krsna mantra. But the warning is that if we keep us on the material platform, then it will be not possible to understand Krsna, His holy name, His attribute, His form, His activities. It will be not possible.

From Srila Prabhupada's lecture on Srimad-Bhagavatam 6.1.15 — June 28, 1975, Denver