Prabhupada, Srila Bhaktisiddhanta, Bhaktivinoda Thakura, Vishwanatha Cakravarti Thakura, Jiva Gosvami, Rupa Gosvami, Sanatana Gosvami and Lord Caitanya have all given guarantees that if you fix your mind upon the Supreme Lord, then certainly you will go to Him. We have to cultivate the desire to always remember Krishna and never forget Him. We should be in anxiety if we are not thinking of Krishna. It is very dangerous to forget Krishna even for a moment.
Lectures From a Disciple Vol 3,Proper Attitude, Pg 228, 4th paragraph