For me it was advice from Dan Harmon: “Don’t try to prove you’re a good writer, you’ll never write anything. Try to prove you’re a bad writer and you’ll write everything.” Not perfect advice but it really does help me write when I’m being overly critical of my ideas.
Kind of a numbers game, isn’t it? On top of that there’s the difference between your own taste and whatever taste a potential audience has
Luckily I only write for me; if it was for anyone else I would have stopped!