I like the idea of having an “end of life wrap-up" for half-finished side projects. Rather than just stopping and leaving them abandoned, you make something like a report on what you learned, what you built, and why you're stopping. Then it feels less like you've abandoned something outright.
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I do kind of the opposite, every week every project needs to justify why I should keep doing it and what I learned recently, and if I can't come up with any good reasons or good learnings, I abandon it.