You have to do your own thing ... usually that's bad advice but for people with the temperament you describe I think it's reasonable.

Also a lot depends on expectations and finding good partners. In a previous job I worked with another guy as a team. I would start projects and get an MVP out and delivering value - then move on to the next thing. He would go through and essentially rewrite them to be high quality, solidly engineered products, well integrated with the rest of the stack.

We both got to do what we enjoyed and were good at: I am very fast at breaking new ground and delivering new value, and find engineering a bit boring. He was very good at improving existing systems, but too slow and plodding to try out new ideas effectively.

I don't think so, most teams never do the last 10% on any project ever. They pick the low hanging fruit with the first 80% and if they are thorough they might bring it up to 90%, but 100%? I've never seen such a software project.

And those who aren't like that by nature are much less useful I suppose?

For side projects, I think there is some value in not being concerned about finishing them. If you're doing them for enjoyment then they shouldn't feel like a job.

But I find defining exactly what done will be on a personal project helps a lot to get completed. I define features are the minimum necessary and once I reach those features I immediately switch to trying to release it. Releasing is always a lot of work so it's easy to put it off forever while constantly iterating on a product. But actually releasing gives a good feeling of accomplishment.

Here's a couple of thoughts. Sometimes not following through might not be about feelings or at least not directly. If you do a project to learn some new tech then the project is not about what it does but about how to do it. So make sure you pick side projects that you think need doing. Find a partner or a group to do the project with or create some way that you make yourself accountable for it's completion. Who are your projects for? If it's for yourself, then is it something you really want or maybe just an idea? If it's for somebody else or some group then create a connection to that group or some people so that you know who you're making it for and include them in the project. That way you have someone to deliver it to and to continue to support. Lastly, maybe it's a decision issue. Maybe you just never really completely decided to do it. How do you know when you've decided to do something?

When I get stuck on projects that are very meaningful to me, I chip away at the pieces I don't want to do and allow myself to take as long as I need to complete them.

When I get stuck on projects that are not so meaningful to me, I reduce scope.