Take some advice here. You can actually beat most nightmares. They usually have some puzzle to solve, or a way to clear them. If you do, they can give you a hefty buff, such as waking up with full hunger and sleep.
Yeah, I do as well, but if they're gonna keep showing up, might as well beat one and sleep another time. I believe it is just chance to have a nightmare, and you are getting unlucky, so maybe it's best to beat one and try again when you get tired again.