A good tip for side projects is to build stuff that is actually useful to you and to make them ZeroOps (no maintenance required). If you find yourself waiting to add a feature and it's not easy to change (ETC) [1] then it's a good moment to stop and how did you lose control of the software.

This applies to all software projects except for the "useful to you" part, which turns into valuable to "your/the business"

[1] https://youtu.be/c8AzqMr87gQ