I don't have this problem myself. I actually rarely remember my dreams anymore. However here are links to 4 articles, from PsychCentral's archives, that talk about nightmares & how to resolve them:

More Than a Dream: The Science Behind Nightmares | Change Your Mind, Change Your Life

How to Eliminate Recurring Nightmares

How to Have Sweet Dreams | Reaching Life Goals

The meaning of your nightmares | Unleash Your Creativity