Sree Sree Guru Gaurangau Jayatah!
Bhagavad-gita (18.66) states:
sarva-dharman parityajya mam ekam saranam vraja
aham tvam sarva-papebhyo moksayisyami ma sucah
"Abandon all varieties of religion and just surrender unto Me. I shall deliver you from all sinful reactions. Do not fear."
Krishnaika-sharana, or surrender to Lord Krishna, is the only means of crossing over the ocean of birth and death (samsara). Performance of one's duty, simple morality, development of bodily or mental powers, acquisition of material knowledge, detachment from material things or even the knowledge that one is a spiritual being cannot bring about realization of God. The vision of God is proportionate to the degree of bhakti or love for Him in one's heart. Lord Krishna says in the Bhagavad-gita (18.55):
bhaktya mam abhijanati yavan yas casmi tattvatah
tato mam tattvato jnatva visate tad-anantaram
"One can understand Me as I am, as the Supreme Personality of Godhead, only by devotional service. And when one is in full consciousness of Me by such devotion, he can enter into the kingdom of God."
--- Jagad-guru His Divine Grace Srila Bhakti Ballabh Tirtha Goswami Maharaj