I think that at least partly the reason a hangover happens is because your brain adjusts to the alcohol, a downer and compensates for it. Once the alcohol is gone it takes a while for your brain to 'slow down' back to normal. Along those lines I think that's why a lot of people say a drink in the morning helps, bloody Mary, hair of the dog, etc. With that in mind, I've found that a xanax or other type of benzodiazepine with some Gatorade and some ibuprofen / naproxen does wonders in the morning. If you don't have access to a prescription drug like that, valerian root or l-theanine work to some degree as well.