By chanting Krishna’s names, one will be transferred to the supreme planet, Krishnaloka, without a doubt.
Bhagavad-gita 8.7,
Srila Prabhupada
Remembrance of Krishna is not possible for the impure soul who has not practiced Krishna consciousness in devotional service. Therefore, one should practice Krishna consciousness from the very beginning of life. If one wants to achieve success at the end of his life, the process of remembering Krishna is essential. Therefore, one should constantly, incessantly chant the Maha-Mantra — Hare Krishna Hare Krishna Krishna Krishna Hare Hare, Hare Rama Hare Rama Rama Rama Hare Hare. — Bhagavad Gita As it is, 08.05.
The chanting itself purifies us and as the heart becomes purified, the Holy name is revealed to us as being non-different than Lord Krishna.
Our spiritual progress depends on service attitude and our sincere chanting.