By performing Vedic ritualistic activities, by giving money in charity and by undergoing austerity, one can temporarily become free from the reactions of sinful activities, but at the next moment, he must again become engaged in sinful activities. For example, a person suffering from the venereal disease on account of excessive indulgence in sex life has to undergo some severe pain in medical treatment, and he is then cured for the time being. But because he has not been able to remove the sex desire from his heart, he must again indulge in the same thing and become a victim of the same disease. So medical treatment may give temporary relief from the distress of such venereal disease, but unless one is trained to understand that sex life is abominable, it is impossible to be saved from such repeated distress. Similarly, the ritualistic performances, charity, and austerity which are recommended in the Vedas may temporarily stop one from acting in sinful ways, but as long as the heart is not clear, one will have to repeat sinful activities again and again. This sinful desire-seed can be removed only by achieving Krishna consciousness. And this can be accomplished very easily by chanting the maha-mantra, or Hare Krishna mantra, as recommended by Sri Caitanya Mahaprabhu. In other words, unless one adopts the path of devotional service, he cannot be one hundred percent clean from all the reactions of sinful activities.
Source: A.C. Bhaktivedanta Swami Prabhupada (2011 edition), “The Nector of Devotion”, Page 6