My Granny once told me that if I was scared of robbers coming in at night to sleep with a knife under my pillow.
So every night I made sure my trusty butter knife was under the pillow. I thought it was a superstition thing that worked. When I grew up I noticed Granny slept with a sharp knife under HER pillow.
A childhood belief about criminals

others believed things like this
- I used to believe Chucky would come out of my toilet, stab me with a knife, and kill me. :(
I hate Chucky. — Bijan - I used to believe in Perez mause when my teeth fall, I put them under the pillow to see what happened— AyrtonZ01
- My sister used to sing Kylie's "cheese on my pillow", somehow tears works better.— Tom
- when I was little I believed that if I put a white stone under the pillow with my tooth I make more moneyAnon
- My nephew refuses to put his tooth under his pillow in case the fairy burns him with her wand.— Nina
- My Granny said if I drank milk and ate fish at the same time, I would die.Anon