For japa to be an effective means to remember God one more condition needs to be fulfilled.
A strong will to transform oneself: Sri Ramakrishna teaches that the mantra purifies our mind, but we have to struggle to grow in purity and not let our mind slide back to its old ways. Even if we have done something wicked we should not dwell on the past, but dwell in the present, be steadfast in our spiritual practice and make an agreement with God: "If a man repeats the name of God, his body, mind, and everything become pure. Why should one talk only about sin and hell, and such things? Say but once, 'O Lord, I have undoubtedly done wicked things, but I won't repeat them.' And have faith in His name."
Weak-willed people often go back to their old undesirable ways. Sri Ramakrishna teaches that a seeker ought to exercise his will and steadfastly practice spiritual disciplines without giving in to weakening thoughts: "Suppose a man becomes pure by chanting the holy name of God, but immediately afterwards commits many sins. He has no strength of mind. He doesn't take a vow not to repeat his sins. A bath in the Ganges undoubtedly absolves one of all sins; but what does that avail? They say that the sins perch on the trees along the bank of the Ganges. No sooner does the man come back from the holy waters than the old sins jump on his shoulders from the trees. (All laugh.) The same old sins take possession of him again. He is hardly out of the water before they fall upon him. Therefore I say, chant the name of God, and with it pray to Him that you may have love for Him. Pray to God that your attachment to such transitory things as wealth, name, and creature comforts may become less and less every day."
This form of devotion finds expression as worship of God's feet in temples and in our personal shrines. There is however a wider implication of this practice of devotion. According to Vedanta, God does not create the universe and living beings out of something external to Him, but projects them out of Himself, enters into them, and pervades them. He is both the manifest and the unmanifest. (See Taittiriya Upanishad, 2.6.1) Hence service to living beings offered in a spirit of worship of God, who dwells in them, is also padasevana.
Swami Vivekananda taught this kind of worship as a potent form of spiritual practice for the present time. He called it Shiva-jnane jiva-seva (service to beings looking upon them as manifestations of God). He said, "You may invent an image through which to worship God, but a better image already exists, the living man. You may build a temple in which to worship God, and that may be good, but a better one, a much higher one, already exists, the human body." Swami Vivekananda spoke of four kinds of service.1. Service to the physical dimension of living beings, which assumes the form of the gift of food, clothing, and shelter. 2. Medical help, which consists in saving or prolonging a life. 3. The gift of ideas, or the gift of education, by which the recipient is able to think for himself, become self-reliant, and improve the quality of his life. 4. Spiritual help, which shows the recipient the way to God-realization, or discovery of his inner Self.