I used to belive that there was an evil man living in my mirror called "FRED" who watched me as I slept - who was basically an evil man (ie - the old man from Poltergeist 2/3 - that movie scared the crap out of me!)
Anyway - I am now 25 and I dont have a mirror in my bedroom, and if I am in a room with one I have to cover it with a towel.
A childhood belief about mirrors

others believed things like this
- I used to believe that my reflection in the mirror was my evil twin that always had bad hair. XDAnon
- when i was young i used to believe that my image on a mirror would come to life if i broke the mirror.Anon
- I used to belive that teachers were evil.....that why they made us do homework.— Lindsey
- I used to think an evil spirit type thing called Wango lived in my dog. I was terrified of that dog.— Franklin
- I used to think that if a mirror with me in it breaks, I break.Anon
- I used to believe that there was a person in the mirror who looked exactly like meAnon