For instance: I get night terrors. The kind where it almost seems as if I'm awake but something goes horribly wrong, in ways it shouldn't even be able to, and then I “wake up”... but, of course, I actually don't. And it goes on in a kind of loop, where I'll think I woke up again and again only for it to turn out I'm still trapped in the nightmare, a prisoner of my own mind.
It happens to all of us, though, to an extent - there was probably a time you mistakenly thought you saw someone out of the corner of your eye, or that you heard your name when no one actually said it.
. . .
So, uh...
There's this idea I heard a while back that's never fully left my head since - that the only thing you can ever be fully sure exists is your own mind. That there's always a chance, however small, that everything else is just an illusion, a figment of your imagination. After all, how much trust can you really put into your senses, when they've fooled you so many times before? Sometimes, I wonder about that. Maybe more than I really should.
Dreams feel pretty real in the moment, don't they?