It's interesting, for myself I haven't had an actual 'nightmare' since I was a kid... and even as a kid, I can only think of one or two true nightmares. These days, dreams that I think 'normal' people would consider a nightmare/scary, I don't... I sometimes think it's because I'm aware it's a dream. So I'm honestly curious to see what will happen. I was even killed in one of my dreams a year or so ago, which was unusual/new, but I wasn't scared/didn't think it was a nightmare, because I knew it was a dream and again, I was curious... it was like..hmm, I've never died in a dream before, this is weird... what will happen? [and I presumably died, but I awoke shortly thereafter, or viewed my death from above (can't remember anymore)...sometimes I'm viewing things as if I'm behind a camera] In another dream it was implied something rather violent was going to occur to me, but I didn't actually experience it /didn't consider it a nightmare... again, I knew it was a dream, so wasn't as impacted by it I guess?
[Note: these more negative themes are few and far between in my dreams..not a common occurrence]