Don't stress out over these things. Some people garden. Some people collect stamps. Other people tinker with cars. And some people tinker with software. That's all a side project is. I make a point of going outside on a weekend and get some time away from my keyboard as well. There's nothing like a good break from coding to get some fresh inspiration and ideas.

If you are doing this for your own entertainment and learning, take it as far as pleases you. I have plenty of half finished things. I like picking one and doing some 'gardening' when I feel like it. Sometimes when I have low energy and I need to snap out of that, I just start doing simple stuff. Maybe I'll update dependencies on a project I haven't touched for ages. Or there's a bit of documentation that annoys me and I fix it. I'll see what needs doing, can use improving, etc.

There's a system to my madness where sometimes I find a use for disconnected bits of software in a business context. And sometimes that never happens and that's fine too. I abandon things as well. Mostly if I don't enjoy working on something, it just gets less and less of my attention. I have well over a hundred github projects at this point. Only a few of them have any traction at all. But once in a while I'll get a random issue report or PR on one that I haven't touched in years and that's all it takes for me to pick up where I left off.