When I was 3 I used to believe that when two mirrors face each other causing that effect where it looks like a neverending sequence of mirrors, that it would be possible to fall into the mirror and be trapped in there, so every time I saw that in the bathroom when the mirror on the door and the bathroom mirror faced each other, I would run.
A childhood belief about mirrors

others believed things like this
- 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'm scared of mirrors because I think that there are ghosts in mirrors— est
- When I was little I was conviced if you said twinkee in a mirror 3 time a foot would appear. Anon
- I had a fear of seeing a person in the corner of the mirror(most of the time a morlock)— Shane
- 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