One’s main purpose in human life should be to purify his existence and achieve liberation. As long as one has a material body, one is understood to be impure. In such an impure, material condition, one cannot enjoy a truly blissful life, although everyone seeks it. Therefore Srimad-Bhagavatam (5.5.1) says, tapo divyam putraka yena sattvam suddhyet: one must perform tapasya, austerity, to purify his existence in order to come to the spiritual platform. The tapasya of chanting and glorifying the name, fame and attributes of the Lord is a very easy purifying process by which everyone can be happy. Therefore everyone who desires the ultimate cleansing of his heart must adopt this process. Other processes, such as karma, jnana and yoga, cannot cleanse the heart absolutely.
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From Srila Prabhupada’s purport to SB 6.2.12