Just as we cannot practice devotional service except by a devotee’s mercy, so we cannot gain spiritual strength except by a devotee’s mercy. In order to have the strength to see Krishna and to enter the spiritual world, we must firmly hold on to the instructions of the Lord’s devotee. Srila Prabhupada gives the example that if we are drowning in the ocean, we can only be saved by someone who is not drowning. If that person throws us a life preserver, he or she can pull us out of the ocean as long as we don’t let go. We must hold on to the mercy; that much we have to do. If we do not hold on, we will never be pulled out. Thus if we want to come to the stage of devotional service, we have to hold on tightly to the Vaisnavas’ instructions by constant remembrance and constant endeavor to apply them. Only then will we find the spiritual strength to allow ourselves to be rescued.
(LFD, Vol2, Spiritual Strength in Executing Sadhana-bhakti, Pg 48, last paragraph)