We have learned in our experience with demons over the years that they are legalists--they cling to the letter of the law, not the intent of a sincere person's heart. For example, we once cast a spirit of nicotine out of a man who hadn't smoked in years. He had changed his lifestyle in obedience to God, but because he had not specifically repented, renounced the demon and cast it out, it remained, hoping to trip him up again in the future.

Repentance is a necessary part of deliverance. Where there is no repentance there is no deliverance. As out text says, godly sorrow leads to repentance and repentance leads to deliverance (the word "salvation" in the original Greek covers the whole arena of healing, deliverance, and freedom available to us in Christ, and is just as properly--perhaps more accurately--rendered "deliverance"). If a person has not repented, then he is still working on the demon's side in that particular area; though he may be remorseful of certain aspects of the bondage, he is still not forsaking the sinful behavior that brought it on. In order to get deliverance from demonic affliction, the individual has to repent, out loud, to the Lord, and ask forgiveness. Even if it's assumed that repentance has taken place, for the sake of the legalistic demons, make it just as clear as possible by going through a prayer of repentance.