As long as I can remember I've had this thing where my brain constantly turns stuff that looks unusual and is usually dark in color (e.g. a crumpled dark towel in the bathtub, my black printer with the tray extended, a pile of laundry on the floor, a weird shadow...) into something terrifying, like a monster, a person or an animal and this gets turned up to 11 at night. The same thing happens with sounds.
I'm in my mid 30s now and it never went away. I still sleep with a plushie because I feel like it will "protect" me from the monsters. Getting a dog also helped immensely. Watching scary movies exacerbates it, so I completely gave that up. I have good days and bad days. On good days I can go down to the basement with headphones on and do the laundry no problem (the trick is not to "think" about it), other times I will get up to pee at night and run back to my bed in a complete panic, like physically filled with absolute dread, so bad I want to crawl under the blankets and cry.
I used to write horror stories about it, thinking that would be cathartic, but it actually made it worse. I tried talking to a psychologist about it when I was a teen. She said it's probably just overactive imagination but I shouldn't tell it to a doctor, because they might misdiagnose me with psychosis (I was in treatment for panick attacks at the time, which retrospectively probably were caused by the pressure I was under to mask my ADHD in high-school). So I've been afraid to mention it to a professional since.
Now I'm late-diagnosed with ADHD and I assume these terrors come from my brain free associating in the wrong direction, especially when it's tired. I've also found that it gets worse in places I am familliar with. Like, sleeping at a new place doesn't usually trigger it. Maybe it's the novelty of the new surrounding, keeping me from free associating? I don't know anyone else who has had this experience at this level. Any takers? Any explanations?