Atonement or prayascitta may remove reaction to sin, but it doesn’t remove DESIRE to commit sin. THAT is only achieved by pure devotional service. Sukadeva Goswami explains this nicely in text 11, Chapter 1, Sixth Canto of Srimad Bhagavatam: “Thus even though one may superficially seem pious, he will undoubtedly be prone to act impiously. Therefore real atonement is enlightenment in perfect knowledge, Vedanta, by which one understands the Supreme Absolute Truth.”