If you wait for proof before you believe in yourself, you’ll never go out and collect the proof.

The evidence you are waiting for is produced by the attempts you are postponing, so the whole thing sits in a loop. Belief has to run slightly ahead of proof, or nothing gets started. That does not mean pretending you are already good, only acting as if it is worth finding out, which is a smaller claim and enough to get you moving.

Borrow from something nearby that you did manage. You learned that other thing, you got through that other week, so the odds here are not zero. Then take one step that generates actual evidence: enter it, ask, submit, show up. Evidence collected beats belief manufactured.