You've got a great idea for a play. You research how to write a play, maybe you take a couple of classes, and you read a bunch of plays. Man, that idea you have is so great you just like to flash it through your mind over and over. Parts of it are vague, sure, but it's the idea of the century! You tell people you are working on a play. They are impressed - you're a writer! They ask you what it's about. You reveal parts of your idea.
You've never written a word of it. It's all still up in your head. Why? Because that's where it's safe.
On the page, it might take another turn. The idea might change. The characters might speak for themselves. In your head, every detail is just the way you want it. Nothing changes. Everything stays the same. There is no risk.
Your idea is a character standing by a door. She's got her hand on the doorknob, but she's not allowed to move. She just stands. There is no action.
If you don't write, you're not a writer. I don't care what kind of writerly outfit you wear, how quirky you are, how much coffee you consume, how misunderstood you feel. Write. Let yourself write badly. Don't tell people about your idea, write your idea. Let it take on the life it was meant to have, not the one that is safe. The best writers are those who write all their ideas - the good, bad and ugly. Eventually one of them sticks.