This is the mentality of one who is becoming a pure devotee. When one is elevated to the platform of devotional service by the grace of the Lord and the spiritual master, one first regrets his past sinful activities. This helps one advance in spiritual life. The Viṣṇudūtas had given Ajāmila the chance to become a pure devotee, and the duty of a pure devotee is to regret his past sinful activities in illicit sex, intoxication, meat-eating and gambling. Not only should one give up his past bad habits, but he must always regret his past sinful acts. This is the standard of pure devotion.