Why do we have such terrible nightmares?

Dreams and the rest of the subconscious/unconscious are like a psychological sewer; absolutely Everything ends up there, and it's impossible to make any real sense of it other than a general idea of what might or might not be bugging you. What is known is that when people are anxious about their dreams and obsess about them, they stay anxious and obsessed. (Oh really. Who'd have thought...) People obsess just as much about stepping on a crack or black cats; the superstition is bogus, but the anxiety about it is a real enough burden we're better off without. The real things in your real life are where to put your real attention; bad dreams are things we wake up from and leave behind, like getting over a headache or cold. They happen, but they don't own us any more than somebodys' car horn or a barking dog. Besides dreams, what's really bothering you? That's where to start.