Have you ever had a hangover SO bad that you swore you were giving up drinking forever?
Well some people are doing this for reals because the anxiety of suffering a hangover are so bad, they'd rather not go through any of it.
There are the physical ramifications of drinking too much of course. The headache, nausea, bleary eyes and general overall feeling-like-crap that comes with the hangover, but then there are the mental elements. Did you do or say something stupid, did you embarrass yourself or others? It's a lot to deal with and easy to see why some people would just rather not. More here