I used to have some pretty scary nightmares. Nothing will ruin a good night's sleep quite like a terrifying dream. One way I've gotten over this is to make up a happy story in my head. When I'm laying in bed, before I fall asleep, if I feel like I might have a nightmare, I just make up a nice story in my head to sort-of kick start a good dream. Happy thoughts pertinent to my own life rather than complete fiction tend to work best...
