Not several years, but I have developed side-projects which burned out after a few months. The longest was 2 years. I put a lot of effort into these projects, a

Not several years, but I have developed side-projects which burned out after a few months. The longest was 2 years. I put a lot of effort into these projects, and some of them I don't even really have demos. But, I learned a lot of skills from developing them. Skills which directly saved me time later on. For example, I learned a lot of concepts which were later covered in college classes, so I was able to study less and do homework faster. When I look back, I don't see anything I could've done in that time to help my future self more (except maybe a successful project? Or maybe investing in Bitcoin? ... but realistically, nothing else) I don't regret those "failed" projects at all: in fact, I wish I could motivate myself to do more of them.