New Year's Eve is traditionally a time of revelry and of consuming large amounts of champagne and other alcoholic beverages. New Year's Day is traditionally a day to suffer a hangover.
The pain, nausea, fatigue, and general lousy feeling that are the after-effects of too much booze has such a long history that you would think someone would have come up with a cure for a hangover by now. No one has. There are a lot of potions and procedures out there that are said to cure what ails you the day after, but nothing that has been proven to work.
The typical symptoms of a hangover are headache, drowsiness, dry mouth, thirst, stomachache and nausea, problems with concentration, and anxiety. Generally, these problems show up as the intoxication wears off and they last for a day or so. These symptoms are caused by a buildup of the chemicals that are in alcoholic beverages and the by-products that your body creates as it tries to process the alcohol.
Alcohol (actually ethanol or ethyl alcohol) is converted in the body to acetaldehyde and then to acetic acid. Some hangover symptoms are from the accumulation of acetaldehyde in the body. Many alcoholic drinks contain chemicals call congeners that aggravate a hangover.
Some of the hangover misery is due to dehydration because alcohol causes you to put out more urine. Your blood sugar levels also drop, which adds to your general woe.
The best way to get through a hangover is to just get through the hangover. Most hangover symptoms go away with time. In the meantime, drink plenty of plain water to rehydrate yourself. Take a pain reliever like aspirin or ibuprofen and take it easy for a day. Avoid taking acetaminophen.
Whatever you do, do not rely on the hair of the dog. Drinking more alcohol just delays your hangover.
Because of the dehydrating effect of excessive drinking, you might consider drinking a couple of glasses of plain water along with whatever else you are drinking while you celebrate.
As far as preventing a hangover, there is only one surefire way: Don't drink.