Growing up a catholic, when I was 7 years old, it was time for my First Communion.
On this occasion all the kids of my age went to a special mass and they get to drink some diluted sacramental wine for the fist time.
We kids were standing in front of the altar, I was the farthest on the right. The priest gave the goblet to the kid at the left, everone drank a bit and passed it on. When it was my turn it was already empty.
As I didn't get to drink, I was afraid this would render the whole initiation invalid, and that with this formal error in my First Communion, I might be turned down at heaven's gate.
A childhood belief about afterlife

others believed things like this
- I always thought there was a drinking age for coffee, because it was an adult drink like beer and wine.Anon
- I used to believe that men drank beer and women drank wine. Anon
- I used to think that if you mixed a diet drink with a regular drink, it would explode. Anon
- I used to think that apple juice was beer and I'd drink it all the time and pretend to be drunk.— Dee
- I didn't quite grasp the concept of time zones, and thought that Chinese kids went to school at night.— Giselle
- I believed Dr. Pepper was pepper-flavored medicine and was afraid to drink it.Anon