Devotional service eradicates the propensity or inclination to commit sinful activity by giving the living entity a superior form of pleasure. Prabhupada gave the example that a young child may be very attracted to play with knives, although it is a very dangerous affair. If the child wants to play with the knife and the parent tries to take it away from the child, the child will grab the knife in an attempt to keep it, and it becomes even more dangerous. Therefore, if the parent offers the child a nice, colorful toy, then the child will become attracted to the toy and will drop the knife. Similarly, for a person who has the bijam— the inclination to engage in sinful activity—when he experiences a higher pleasure in Krishna consciousness, he will give up his inclination to engage in those sinful activities, which are a cause for his suffering.
LFD Vol 3,Uprooting Sinful Activities, Pg 204, 2nd paragraph onwards