I believed that when a baby was born, he could remember his prior life and his time in Heaven in detail but he couldn't tell anyone about it due to lack of communication skills. As he learned to speak the language of his parents, he gradually forgot all of the previous information that would've answered all of the secrets of life.
A childhood belief about reproduction

others believed things like this
- i used to believe i was spongebob squarepants in a previous life.— former sponge
- I used to think life was a dream and I was in heavenAnon
- I used to believe that a life sentece was for when you stay in jail for your whole entire life.— Sara
- I used to believe that my life was a video game with only 1 life and that God was playing it. — Rina
- I used to believe, that I am able to speak every foreign language only by learning "their" alphabet.— matej
- I would speak in gidderish, convinced that it was some foreign language I had never heard of— Molly