One achieves bhakti [love of God] by hearing and chanting about the Supreme Lord's special qualities, even while engaged in the ordinary activities of life in this world.
Yoga means to connect ourself again with God, or Krishna. This practice of yoga, always thinking of Krishna, is very easily accomplished by chanting Hare Krishna maha-mantra, if you chant Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare, Hare Rama, Hare Rama, Rama Rama, Hare Hare. Twenty-four hours it can be practiced. There is no expenditure, there is no loss, but the gain is very great.
From a lecture by Srila Prabhupada, Bhagavad-gita 7.1 — Durban, October 9, 1975
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.
Practical action is the best way to show our determination. So while chanting, we should show our determination to be attentive. This attracts Krishna's attention.
By chanting of Hare Krishna, you have the Lord with you and He satisfies you. He pleases you. You are pleased with your Lord. He is also the Lord of your heart.
The chanting of the Hare Krishna mantra is recommended even for persons who commit offenses, because if they continue chanting they will gradually chant offenselessly.
Purport on Srimad Bhagavatam 6.3.24