working long hours does not mean you dont take regular breaks. its like marathons, you dont run at full speed when you know you will run for a long time.
"You haven't taken vacation? Nah I can take it whenever! It's not big deal! My team needs me and I love my job!"
I believe he was referring to it can be dangerous to view your work as something you love. Make sure to give space for your loved ones and your own free time and be conscientious of that. Naturally, your company will do it's best so that you do love your work, but understand there is more to life than that.