I've had this same experience with writing music.

The trick isn't to be brilliant and pop out a masterpiece. The actual trick is to be able to generate enough variations that you can sort through them, cull the promising from the unpromising, rearrange them in various ways, stitch together the seams, and then sit back and lean on your personal aesthetic to decide whether what you've cobbled together makes you want to share it with others, keep chipping away at it, or abandon it altogether and start over (or not).