As a kid I was Catholic and I would pray every night to not have nightmares or at least not remember em. Might seem kinda silly but I think reinforcing that you won't have nightmares might help?

Weirdly enough, what used to help me was putting on a sleep playlist of calming music I loved and falling asleep to it

When I was 16 I took a medication that made me stop dreaming all together and I hated it, I can't remember the name, but usually I get up for a bit, grab a glass of water, and listen to calm music, then go back to sleep.

When I wake up from vivid nightmares, I find that light is my best friend. I'll turn on the lights and find 5 beautiful things to look at, or I'll find a funny video on my phone. After, I like to ask myself what my subconscious was trying to communicate... Sometimes after a dream, nothing/everything feels real so that helps me distinguish my real emotions from the emotional dream