Jnanis always want to be independent from Krishna. Therefore they endeavor on their own to achieve the results of their activities. Devotees, however, always depend on the Lord for His mercy in anything they do. Devotees always base their enthusiasm not on independent endeavor but on faithful dependence on the Lord. Bhaktivinoda Thakura further says in Bhaktyaloka that we should not lose enthusiasm because we have no strength to destroy the reactions of karma. In the very beginning of devotional service the sadhaka must have faith with full enthusiasm.
(LFD, Vol2, Enthusiasm for Devotional Service, Pg 37, 2nd, 3rd paragraph)