I've had two weird experiences, both of which occurred in the same area of my childhood home, one in my bedroom the other right outside my bedroom. I dunno if it was a temporary mental breakdown with vivid hallucinations, but both times I was 100% sober and I know what I saw.
One of them was just a passing guy that I saw out of the corner of my vision when I was reading a book. The other was fucking spooky. I wake up one morning, it was either a weekend or summer because I was nice and relaxed, gonna lie in bed for a minute or two. I have a nice relaxing eye close for a couple of seconds, when I open them there's a woman on my ceiling, directly above me. Best way to describe her is Helena Bonham Carter in the Harry Potter movies, but uglier and older:
She leaves the ceiling and comes flying towards me, I scream and my heart starts pumping. She reaches me and just disappears, I don't physically feel anything, I'm not hurt, I'm just all alone freaking the fuck out. Like what are you supposed to do at that point, tell everyone you saw a ghost? Everyone will think you're either crazy or making it up for the attention.
I've coped with that shit by thinking it was some weird brain thing because I had just woken up, like it was still dreaming or I had fallen back to sleep and had a 3 second nightmare. But I've woken up a lot more times in my life and that shit hasn't happened ever again.