Usually I start projects I want to start, but I tend to finish projects because I have to finish. The necessity/drive to finish can be internally or externally

Usually I start projects I want to start, but I tend to finish projects because I have to finish. The necessity/drive to finish can be internally or externally driven, but there's no mistaking it, so don't sweat what you don't finish. Take it as a signal that you've reached the limit of your interest in that pursuit. Of course, if the issue is something more fundamental (like ADHD), none of this likely applies, and seek help from a professional.