The Fear loves The Blank Canvas. They’re best buddies. Show them who’s boss by deciding “why” before “what”. It will save you hours of frustration.
Where do you want it to be heard? Which situations do you imagine it being played? Who will hear it? Is it a means of self-expression which only you’ll experience?
Be honest with yourself. You might think “I don’t care about playing it to anyone else”, but that sounds suspiciously like The Fear talking. If you have an inkling you might want to put it out there, acknowledge that and go for it. Don’t pretend you’re just doing it for fun. Because if you’re doing it right, often it won’t be fun.
By thinking about your purpose it’s easier to overcome the moments of creative “stuckness” that everyone experiences. And crucially, with a clear outcome in mind at the start you’ll know where the end is, when to ship and when you can move on.