When that ineffable compound of depression, sadness (these two are not the same), anxiety, self-hatred, sense of failure and fear for the future begins to steal over you, start telling yourself that what you have is a hangover. You are not sickening for anything, you have not suffered a minor brain lesion, you are not all that bad at your job, your family and friends are not leagued in a conspiracy of barely maintained silence about what a s**t you are, you have not come at last to see life as it really is and there is no use crying over spilt milk.
Hangover cure: Rigorous sex, hydration, hot bath, then "go up for half an hour in an open aeroplane. (needless to say, with a non-hungover person at the controls)."
He who truly believes he has a hangover has no hangover.