When I was a younger writer, I was convinced that someone had stolen my idea. Now, that isn’t my concern anymore. What no one can steal, is your perspective. Take the following comics as an example: Garfield, and Get Fuzzy. Same setup. A neurotic man has a dog and a cat that “talk” to him and each other. Although they have the same premise, they are very, very different.
Someone stole your idea for a novel? I’m sorry. Took your screenplay? That’s awful. Write it, draw it, make it anyway. Remember the story of the goose that laid the golden eggs, only modify it. If someone gets a golden egg, what they don’t have is you, the goose who made it. You can always create more. Someone stealing from you means that you have something worth saying, and eventually, someone is going to start listening. You may never be a New York Times best seller, but the more you invest in your art, the more of a master you become.
As I write, this proverb came to mind:
“Do you see someone skilled in their work? They will serve before kings; they will not serve before officials of low rank.”
The important thing is to keep creating. You’ll have bad days, block, things that don’t look right, but if you persist, you will repay yourself in your craft.
They can’t steal your perspective, and they can’t copy your life that colors your work.
Hope that helps.