The devotees can constantly think of the object of worship, the Supreme Lord, in any of His features, Narayana, Krsna, Rama, etc., by chanting Hare Krsna. This practice will purify him, and at the end of his life, due to his constant chanting, he will be transferred to the kingdom of God. Yoga practice is meditation on the Supersoul within; similarly, by chanting Hare Krsna one fixes his mind always on the Supreme Lord. The mind is fickle, and therefore it is necessary to engage the mind by force to think of Krsna. One example often given is that of the caterpillar that thinks of becoming a butterfly and so is transformed into a butterfly in the same life. Similarly, if we constantly think of Krsna, it is certain that at the end of our lives we shall have the same bodily constitution as Krsna.