Good question. A series of things led me to quit (extra weight, horrible deathlike hangovers, alcohol induced depression, profound lack of satiation when I drank). I think too it was the realization that I was not "growing out of it", and in fact was actually getting worse as I got older. I did not want to continue my drinking problem in my late 30's or 40's so I quit for good at the end of my 36th year.