Basically a pervasive sense of your own mortality, usually coupled with the heebie jeebies (non specific paranoia and a sense of just missing things at the edges of your vision). Apparently something to do with the low blood sugar, common or garden sleep deprivation and that alcohol can cause acute depression like symptoms in some chunk of your brain or other. It's insidious and generally will last all day, long after the more physical symptoms have gone. Sleep is the only cure, though a modest hair of the dog can help alleviate it. I'll usually get it if there has been more than one session within a few days, a 'compound hangover' if you will. In this case I've had a couple of leaving drinks with different friends during the week and a fairly hefty one with my brother. Add to that stress from moving and my little one had an operation a week ago and I'm vaguely amazed I haven't fallen apart at the seams.