Personal life hacks:
1) All the folks telling you that diet and exercise will magically make things better are actually right in micro scale. (You can't pushup your way out of being a salaryman but it is very hard to not get a QOL boost from reguar exercise.) Blew my mind to experience this since I had always assumed it was social signaling.
2) Your startup will always send signals that it really needs you. Consider making a commitment to maintaining family/friendship/church/whatever ties so that you can maintain perspective on how much the bat signal going off really matters.
3) You'll tend to end up like the folks you hang around with. If you steep yourself 100% in startup culture, you'll tend to pick up its cultural pathologies. I mean, do your five closest friends all overwork? That might be why seeing half days off as a luxury item became your new normal. Consider reconnecting with old friends or broadening your social circle.