[wool_gather]

At least for me a large part of my choosing my career (software development) is because I love writing code. There's a huge mental difference for me between spending time writing code for myself, to learn or explore, and being at the keyboard for my employer. The complete self-direction in the project changes the character of the time. It really is a different headspace, and I don't think it's quite fair to say that it's still "working", in the sense of it being a job.

In my experience, the problem with overworking is not the activity itself. It's the mental state of doing a thing because of some sense of obligation, duty, or politicking/competition (or maybe threat, if you're doing it because you're anxious about job security).

Now that said, I totally agree that physically doing the same activity for endless hours every day is not going to be healthy -- including mental health. I think you're totally right to suggest balancing out job tasks with contrasted activities. It is good for your body, and keeps you from getting stuck in ruts mentally. As appealing as it sounds sometimes, I'm not just a brain in a jar. Using the muscles and talking to other humans is also important for being fully human.