Sometimes, when a demon is cast out of someone, the same demon may find its way back into that person again. Some people get confused about this; but it's not a mystery at all. Jesus said when a devil goes out of a man, he goes through dry places seeking rest. When he finds none, he says, "I will return into my house from whence I came out; and when he is come, he findeth it empty, swept, and garnished.
Then goeth he, and taketh with himself seven other spirits more wicked than himself, and they enter in and dwell there: and the last state of that man is worse than the first..." (Matthew 12:44-45).
This is something a lot of people don't understand. It's not enough to cast out devils; you must replace the work of devils with the ministry of angels; you must replace the wickedness that was hitherto in the person's heart, with the love of God! You must teach and minister the Word to that individual; the Word is what now washes him clean and transforms his life.
It's the same thing when dealing with certain habits in your life. Part of our theme scripture says, "be renewed in the spirit of your mind." It's talking about being renewed in the character of your mind. When a Christian has a particular habit, and he says, "I can't stop it; I've tried severally," it's obvious he hasn't given himself wholly to the Word.
Romans 12:2 says, "And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God."
Through the Word, you're able to replace fear with faith, and weakness with strength. With the Word of God, you can do anything, and be all that God wants you to be. Give the Word first place in your life; yield yourself completely to the Lordship of the Word.