An improper desire (επιθυμια epithumia) can start in the corners of our mind. Dwelling upon or entertaining such desires normally intensifies the wrong desire, which, in turn, will influence the heart. Deep Bible study easily explained.
We must never become content with our spiritual growth. Even though we have stopped engaging in serious sins that we committed before accepting Christ, we still need to be careful about avoiding anything that could tempt us to go back to that former life. How can we do that?