Whether you believe you can write today or not, remember: there’s no physical law, not even a mental barrier stopping you from putting pen to paper or opening your phone or laptop and writing.
Start like this: “I am writing.”
Do it now.
Then keep going.
Believe whatever you want. Change your beliefs however often you want. Your innate ability to write is steady.
And if you know that, why wouldn’t you align your beliefs with your innate ability?