At my second startup we had to keep track of how many hours we worked each week. The justification was vague: something to do with a client contract. The numbers each week were public so things got competitive. Developers began working even crazier hours -- noone wanted to be thought of as a slacker. As anyone who has tried to sustain ultra-long work hours knows, things got bad over time: more mistakes were made, people lived in their offices, the place started to smell, external relationships were strained, people got sick easily and still came into the office infecting co-workers, etc. The sad thing was that management didn't recognize that there was a problem. People wanted someone to say "hey, it's okay, you can ease up!" but they didn't. By the time burn-out set in, the level of resentment of the managment team was huge.
Also read Damien Katz's excellent blog about slack
Sometimes I'm hyper focused on code, sometimes I'm not. When I'm not, I try to enjoy the things that actually do interest me and exhaust those interests. So during this period I focused on:
:-) Now, there's a man with his priorities straight. I'd put 'God' in there on mine, but that's pretty close.