Yeah, I don't know. If I love playing guitar, doing it 10 hours a day, 7 days a week, is going to get old. At some point it becomes counterproductive. Sometimes I sit in front of a screen, and I WANT to do something, excited even, but my brain is just not sharp enough.

With coding, it's also a matter of quality of work. You need to step back so you can look at your work with a fresh perspective, and oh, there are ALWAYS horrors you will find, the ones you created when tired.