It's essential to take some time off work. It helps us regain energy and focus.
More importantly, time off work keeps us grounded in the things that are most important to us in life, lest we forget.
Working 12+ hour days is not healthy, and I wouldn't recommend it to anyone. At the end of the day, what we do for others matter most. To me, my relationship with my friends, family, and significant other matter most.
In my opinion, focusing on business and clients doesn't keep me warm at night. And warmth is important to me.