While performing devotional service in the association of pure devotees in full Krsna consciousness, there are certain things which require to be vanquished altogether. The most important thing one has to surmount is weakness of the heart. The first fall-down is caused by the desire to lord it over material nature. Thus one gives up the transcendental loving service of the Supreme Lord. The second weakness of the heart is that as one increases the propensity of lording it over material nature, he becomes attached to matter and the possession of matter. The problems of material existence are due to these weaknesses of the heart.
Ref >> Srila Prabhupada Vani.