How do you stay focused on one project at a time?

What it works for me is write down the plan, without a plan, it's really difficult to finish anything. I had this experience building docxmerge and it took me 1 month and a half. I had a hard time because I was focused only on one project and university, and what happened to me is that I overthought a lot, you got to be very practical for side projects.

Now I'm dividing my time in N projects, I say, I'm going to do whatever I can about X feature for the Y project in N hours, and that keeps me active and motivated through the day.

I'll comment first since it's my post. I've learned a few tricks to keep me going and on my latest project (a photo manager app), I'm almost at a point where I'd like to launch it yet still I struggle to keep going.

As far as my tricks:

1. prioritize dev experience - if it's a pain in the ass to work on, you won't work on it. The more I invest into tooling, the more I end up writing code
2. one project at a time - even if it means I'm not working on anything for weeks at a time, I try to stick to one big objective
3. incremental improvements in the down period, big improvements in the up period - whenever I'm having a bit of hard time focusing on the project yet I still want to work on it, I try to tackle small annoying tasks or refactors. When I'm 100% there mentally and coding-wise, I try to leave the small annoying things alone and tackle big features
4. self-compassion - I try to be kind to myself about not getting stuff done. After all, this is supposed to be a hobby project! And even if it is a side hustle, getting onto yourself won't help.