Never suffered from hangover, but I have read about it. It seems to be mostly dehydration. If you drink one glass of water for each time you urinated the night you drank before you go to sleep I wonder if your hydration level would be the same.

Might be. Think there might be some psychology too.

Sometimes I'll go out to a bar and get absolutely shitfaced drunk (8 double G&Ts, for instance) and wake up the next morning feeling fine. I'll pour myself one drink at home before bed and wake up the next morning feeling like death.

A bit of energy exertion to walk to the bus stop and get home may have made all the difference.