How can I rein in my overactive imagination?

My daydreams run way longer than any I've heard of, and they scare me half to death. My toes always have to be raised or covered because of one of them. It takes my hours to get to sleep, and it's all because of my daydreams. Even if they start out nice, they seldom stay that way. Violence is a main theme, and I'm worried I'm disturbed. Sounds in the night like creaks cause a whole new stream of thinking. Help!