In my experience I've found the best way to combat this is to pick a single thing and then pick a timeframe (something short like a couple of weeks at most) and

In my experience I've found the best way to combat this is to pick a single thing and then pick a timeframe (something short like a couple of weeks at most) and then you aren't allowed to do any other projects until you complete the one you choose or the timeframe expires. This is aided by putting ideas that come up along the way into a journal like mentioned in other comments. For example I want to go back to learning go, and I want to practice foreign languages, and I want to work on small short term schemes. But I decided in mid april to work on a short list of four tasks until may 20th. I can only work on those tasks (unless some urgent work thing comes up). I find this method to be super relaxing because I know that as new ideas come up I can just log them for later and only have a short list of things to think about and work on. It's very freeing.