It IS hard to predict what will do well. Sometimes I spend half an hour on a post and it does better than something I worked on for hours.
But we people are funny. Hard to know what will catch on. No one could have predicted Pet rocks, Tamagotchi, and Fidget Spinners. Writing is the same way, I think.
I’d say don’t try to figure it out. It’s too easy to slide down that slippery slope where you’re trying to write what you think people want to read, instead of writing the things you feel deeply about. I don’t think that ever works out very well. You know?
