It's a shame no one is really talking about the elephant in the room. At the end of the day, most people are working on side projects... at the end of the day.

It's a shame no one is really talking about the elephant in the room. At the end of the day, most people are working on side projects... at the end of the day. If you really want to be effective working on something that isn't your primary thing, it absolutely can't be after a full days work, even if that work isn't very taxing. Your mind needs time to not be working, or at least, not be working on things similar to your day job. Worse, is many people working on side projects are also doing it at the expense of sleep, which is kind of like doubling down on a losing bet. Sure you might get lucky, but you've still got a negative expected value from your time. People get dumb when they're tired, and worse, is they often can't even tell how dumb they've gotten. If you want to work on a side project, you probably don't want to work on it after work. And you probably don't want to work on it on your first of consecutive days off. Even writers who claim to be night owls tend to work on their writing first thing after a good sleep. Also, if you really want to validate this wisdom, I suggest learning to play a competitive game with a ranking system (although you may never get around to your side project if you do...). I would bet dollars to donuts to that you will tend to gain ELO/rating early in the day, and you will tend to lose ELO/rating late in the day. That has held true for me for any game I play seriously. It can be even worse at night, in that as you lose game after game, you start to go on tilt, and try to keep playing until you get that win, or until you gain back the rating you started with. It's absolutely insane, but often not obviously insane until the next morning. Also, probably just take my word on it, and don't game competitively, you're life will be richer without it. Just understand that there is a mountain of evidence that talks about how bad people are at performing when tired, and that the very best artists tend to spend most of their time recovering from their creative endeavors, punctuated by very short, very intense periods of exceedingly high focus.