A semi-relevant anecdote: over the Christmas break (which was > 2 weeks for me), I was pouring 12-14 hours a day into my personal hobby project and didn’t feel tired or bored at all. I literally couldn’t stop working on it.

Now that I’m back at my regular job (which, I must concede, is an amazing job on paper and something I spent a lifetime getting to), I can barely survive the day and have zero energy after 16:00.