Truthfully, I don't think you'll find many responses here of people that can stop at one & are not obsessing over alcohol. I'm here because I can't.
Normal drinkers drink because alcohol although a mind altering 'drug' that lightens the mood of meetings & celebrations and family gatherings. Normal people can have a beer at a ball game without overloading and stumbling up the bleachers. Most normal drinkers can go to a picnic and have a drink and have fun playing volleyball -not vomiting behind a tree. Normal drinkers drink because its a socially exceptable behavior in society.
If someone drank once a month only on a game night but they passed out everytime. I wouldn't consider them an alcoholic but a person that needs to drink less at that particular function and evaluate their drinking patterns. An alcoholics drinking is accompanied by stress, uncontrolable drinking at all hours of the day, unmanagability in life and loss of loved ones and opportunies because of their drinking. Just because you go out once a month and pass out doesn't classify you as a drunk -in my book.
But you could be on the verge of a successful drinking career if you don't pay attention.