Have you ever noticed that about some topics, the same person can tell you completely contradictory things and sincerely mean both of them? I've noticed that kind of tension sometimes and it tells me that there is no simple answer to that particular question - the sweet spot is somewhere in the middle, and in fact might move around depending on the situation.
One of those topics is the idea of how much you should work. There is one side that says that the most important thing is your life: your family, your friends, having time to rest. That side tells us that you've gotta draw very clear boundaries around your work time so that it doesn't encroach on your personal time. You should work 40-45 hours a week, and when you're at work you don't think about home and when you're at home you don't think about work.
There is another side to the story that says that you have to be productive and achieving. You are called to a certain job and you've got to do your very best. You can't be a leader in 40 hours a week, you can't meet your obligations in 40 hours a week, and you can't change the world in 40 hours a week. This side says you need to sleep less and do more. You should do all you can, and when you run out of steam, do just a little bit more to increase your capacity for next time.
What is the proper balance? Neither side is entirely correct, but neither side is entirely wrong either. In fact, when you read them independently, they both seem completely reasonable and inspiring. How do we achieve both of them at once? What is the balance?