Ask HN: How can I pick a side project and stick with it?

I'm a web developer and DevOps engineer. I know a few languages and frameworks very well, I can find my way around with a good deal of other languages and frameworks, and I'd like to learn a lot more.

My problem is that I cannot seem to be able to pick a project (any project) and stick with it long enough to do any meaningful progress, let alone finishing it. It's been several years since I've managed to work on a side project for more than two days continually.

I sit before the computer thinking: I know! I'll write a roguelike in X! Five minutes later, I'm thinking: fuck roguelikes! I'll write a graphical solitar card game with Y! Five minutes later, I don't care for it anymore, and would rather write an isomorphic strategy game in Z.

The same thing happens with tools I might need, applications I think about, experimental stuff, etc.

Has anyone else experienced this, and, more importantly, found their way out? How?