Your mind gradually manages to reconstruct some sort of memory of some portion of the previous night's activities. You need help. A little understanding of what a hangover actually IS really comes in handy here. It means rest and as little nervous stimulation as possible. It also means trying to eat something that will help to replace the nutrients you've lost.
Bananas are great for key vitamins.
Strange but true. This came to me by pure accident. I was a suffering bastard one day following a night of revelry, and I knew I needed some food, but I found myself in a situation where I didn't really have any choice about the lunch that I'd been served. I couldn't believe how quickly I had gone from hangover hell to basically ok. I figured it was just a fluke.