As a child I coped with vivid nightmares by crawling into my parents bed. Worked like a charm (parents are invincible entities that can protect you from anything, up to and including the heat death of the universe).
As a teen (when the above mentioned parental bed stopped being an option) I taught myself to redirect dreams to better endings. Doesn't work 100%, but I can usually get back to sleep within a reasonable time frame. I have tried to explain to DS5 (nightmares, afraid of the dark) how to do it -- not sure it is really working for him at this age.
