Every time a child says, "I don't believe in fairies," there is a fairy somewhere that falls down dead.
Peter Pan by J. M. Barrie.
Children have an amazing ability to believe. They read Dumbo and believe he can fly. They believe there are mermaids living under the sea. That animals can talk. That if you wish on a star all your dreams come true.
Then children grow up.
We don't believe in magic the way we used to as a child. We learn to look for the logical explanation behind the things we don't understand. Sometimes, no matter how much we might want them, we even stop believing in our own dreams.
As a writer, I like to think the only thing that can hold us back is the ability to believe. I need to believe in the words I weave. Believe in the worlds I create. The characters who live there. Because, even though I know they aren't real, I have to believe in my characters. If I don't then why should a reader?
And maybe, when I write, I'm still that child who believes.
So I'll clap for the fairies... just in case.