I got up at 1 and lasted until about 4:30, at which point I faded right out until after 8.
Well--woke up around 7-ish this morning, called off work, had a PB&J, went back to bed and slept another five hours. Sleeping until 1 normally carries a heavy penalty (splitting headache upon waking) but not today, probably because of sandwich.
All I know is, I must've needed that sleep. There's just no two ways about it.
The funny thing is, when I was much younger, I used to be a little curious about the well-known fact that fatigued people make mistakes. It was something that was obviously true, yet I had never observed that behavior in myself.
(It did not occur to me that a) I had never really known fatigue, and b) I might not be wise enough to recognize a mistake even after being rested.)
Well, I'll tell you what--in recent years, I've seen plenty of examples of that behavior in myself. Like the bathroom wall; that part with all the gouges ended up that way because I was tired and couldn't think straight. So the tool would slip and make a gouge, and I'd think, "Well, it's just one gouge," and then a few moments later I'd do it again and think--again--"Well, it's just one gouge," and so on. Presto: the wall looks like a relief map of Hiroshima after the blast.
And you really are incapable of recognizing that you're not fit for duty. Mental fatigue is worse than physical fatigue; at least with physical fatigue your body sends you all kinds of emphatic signals that it is time to rest. But when your brain is tired--well, the brain itself doesn't have a pain mechanism, and you can really grind yourself down mentally before you realize it.
...all of which is meant to rationalize taking an abrupt day off. But I think I made the right choice; my head feels clearer now than it has in at least a couple of weeks.