The “well maybe I don’t exist” thing is actually a pretty long-standing pattern of thinking.
Since I was little, I’ve had a lot of feelings about fictional characters being tortured– those feelings consisting not of sadness and empathy, but of “It’s ok, you can do this! This is easy! You just have to [dissociate]. Ok well maybe you can’t do that, but I could, if I were in that situation I’d be fine.”
Maybe the real source of that thinking was that I couldn’t stand to think of people, even fictional characters, actually being helpless and in pain? Maybe.
Anyway, it’s a thing in my mind. The usefulness, the successfulness, of being able to tolerate anything that’s done to you and re-emerge later when it’s safe.