"So shall my word be that goeth forth out of my mouth: it shall not return unto me void, but it shall accomplish that which I please, and it shall prosper in the thing whereto I sent it." (Isaiah 55:11)
Did you know that the battleground for the problem you're facing right now is in your mind and on your lips? If you'll hit the devil with the Word and cast the care of the situation over on God, you'll win.
Let me warn you though, hanging onto the Word isn't always easy. The devil knows that if he doesn't steal it from you, you'll use it to enforce his defeat.
So don't be surprised if he sends an evil spirit to exalt itself against the Word of God. If you're sick, he may begin to tell you, "You're not healed. You know that healing's not for today. Even if it were, it wouldn't work for you. It might work for somebody else but not you."