Believing in mythical creatures.
Mythical creatures from fairy tales, without thinking about it we say they don't exist. Dragons elfs and gnomes, nobody ever saw them the exist in books and in your head. If they can exist there why can't they exist in 'real life', somewhere deep in the forest or the mountains.
As soon as you're about 8 years old people tell you there all made up. They will fill your head with things they want you to know. And suddenly all the things you ever believed in are bullshit.
I think it is time to find out for yourself what did and didn't existed. Explore the world and keep believing in what you think is true!