I see what you mean.
I think it really depends... I mean it could be that from the day you were born what you most wanted to do was say, paint, or act. If you can make a career out of it, I can see it becoming your whole life, you know?
On the other hand, when it starts as a way to make money, not a passion, not something that fulfills you and is your purpose in life, then making it the center of your life might be a bad idea I guess. Because that would become stressful.
I do think for most people the off time is more relaxing. Whether you love your job or not, it's still a job, so you probably have deadlines, people to pleases, things to follow, etc. Once you're off work though you don't have to worry about this stuff.
But for some people, their job being their life makes sense to me. Imagine going to various countries and taking pictures. That sounds like a vacation, right? Well that's some people's job. So yeah, sometimes it does make sense to me. But I agree a job will always have some degree of stress due to being a job.
Anyway, I agree with your message that you shouldn't forget to live and do things you enjoy in your free time rather than work constantly or be in a "work" spirit even on your time off. But... I still think it depends on your job. I can imagine any creator being able to just turn off their inspiration because they're on a day off, you know?