I feel this too, and I've learned to accept that this is just the way my brain works. Once I've lost my motivation for a certain project there's really no point trying to force it back, and besides, this isn't such a bad thing. The whole point of a side project is that I can work on what I want, even if that means doing something new every 4-6 weeks.
I create a "project" in my to-do list app for each side project, and dump every little idea I have in there while I'm excited and switched on about the idea. When my motivation ebbs and eventually returns (months or years later), I have a low-friction starting point to jump back in, which makes all the difference.
Jumping into a months-old codebase _and_ having to figure out what to build next usually means I feel a bit discouraged and never really get back to that project.
I create a "project" in my to-do list app for each side project, and dump every little idea I have in there while I'm excited and switched on about the idea. When my motivation ebbs and eventually returns (months or years later), I have a low-friction starting point to jump back in, which makes all the difference.
Jumping into a months-old codebase _and_ having to figure out what to build next usually means I feel a bit discouraged and never really get back to that project.