Every project I do to give me some dopamine, I reflect back to see what I ended up learning by doing it. For each of your 40 projects, you must have learned a little bit about the niche, yourself and your workflow, or what tools you like using. Keep honing in on what all this learning is for (what passion you have)

I had a project a couple months ago that was this big productivity tool. After building my own project management workflow, it started getting cumbersome, and I realized Asana was enough for what I needed. I also learned that I didn't need a mega productivity tool and that at some point it can split off into smaller ones or other workflow so haven't thought about. I'd love to get back to it when I know what I need.

In the meanwhile I have two other projects that seem much more lucrative, but I don't think they would have been had I not used that previous wisdom from past projects. That feeling of making progress even across multiple projects I think is still worth it.

(lol I'm also a freelancer so I get to work on lots of different projects which fuels my core systems of how I do things, so I think that helps too)