A hangover is your body's way of saying it has been poisoned by alcohol and is going through the effects of the withdrawal. Hangovers can occur approximately 8 to 12 hours following the last drink and can range anywhere from fatigue, depression, headache, thirst, nausea, and vomiting.
The only way to get rid of a hangover is to give your body time. You can help your body clear the alcohol out of your system by keeping your body hydrated with water and other caffeine-free, non-alcoholic drinks. Eating something before bed may help as well.