Last month, my wife and I found ourselves in a disagreement about whether or not our apartment was clean enough for guests -- the type of medium-sized disagreement that likely plagues all close relationships. In the midst of it, there was a lull and, feeling exhausted all of a sudden, I got up and left the living room. In the bedroom, I immediately fell face down into the sheets. The next thing I knew it was 20 minutes later and my wife was shaking me awake. I hadn't meant to fall asleep; I just felt so fatigued in that moment that there was nothing else I could do.