Haven't really read a lot of the responses, fyi.

I have a lot of random nightmares. I never change the ending... but when I wake up, I do tend to go over them in my head (this depends on what TYPE of nightmare I just had... if it invovled people I know in real life then I just ignore it as best as I can, but if it's more of a "story" sort of nightmares then I think about it... sometimes I'll end up finding some humour in it). Well, with my story-esque nightmares, I usually wake up before there's any clear "finish", so I treat it like I would a story I'm writing, and I think about what was going on and what was maybe going on behind the scenes in th story that I wasn't privee too, and then think about how things would have gone if I hadn't just woken up at the scary point..... and while doing that, I end to end up continuing it into a less horrific ending.

So while I don't change anything, I do continue it until it gets to a more satisfactory ending.