I mean, guitar for instance. Regular practice is good, but if you aren't having fun while doing it, it just means you feel like you are working during your free time. If you program for a living, doing it in your free time might feel like work even if you enjoy it. And so on.
I'll also mention that when trying out new things, it doesn't matter if you finish a project. You tried something, might or might not have liked it, and possibly figured it wasn't for you or that you rather like spending free time doing other things.