Not drinking the amount of alcohol that is usually needed to get wasted the night before, therefore your body feels teased and weak the next day due to the lack of alcohol consumption. In 90% of cases, consuming an alcoholic beverage the next morning as soon as possible will reduce symptoms.
Jack: "Why am I so sick ? I didn't drink THAT much last night..."
Jill: "You've got an alcohol deprived hangover, stop being a wuss and drink like your supposed to"