I used to believe that people who were in their "early twenties, etc." or "late twenties, etc." actually aged either slower or faster than everyone else.
A childhood belief about getting older

others believed things like this
- i used to think that the faster you go in your car, the faster the car radio went.— Matt
- When I was a little kid I thought that salt was some form of an aged sugar.— Jodie
- We used to think that if you ran swinging your arms around, you would run faster. — Christine
- Red shoes make you run faster. — Ann B.
- ... i used to believe the more stripes my pair of sneakers had, the faster i would run ...— wilbur
- that if you had fun, time would literally pass by faster— paul