Once I was having a dream. I don't remember the dream, but it wasn't a pleasant one (not a nightmare, just not a pleasant one).
Suddenly, I realized that I don't have to have this dream if I don't want to. I didn't realize that I was in a dream, or that I could control it, or could have a different one – no, none of that. I just had this thought arise from somewhere that I don't have to have this dream if I don't want to.
Not knowing what else to do, I started focusing on my breath. And, really, I stopped having that dream. After a while, I dissolved into a dreamless sleep.
I woke up. And wondered if that trick works when I’m awake.