This is probably running into a different issue, which is most people have a finite amount of programming (or intense concentration work) in them per day. For me that's 3-4 hours, for most creative people that number is pretty similar. Beyond that you get vastly diminishing returns and worse trying to do a "side project" involves a massive context shift that is mentally exhausting in of itself.

Once I accepted that after 3-4 hours (well realistically about 6 when you factor in breaks) I'm effectively done for the day my stress levels went way down.