What I always tell myself when I think "Gee, I could have just one" is... you are lying to yourself and you know it. You NEVER want just one. You want to be drunk. Just one or two is more stressful than not having any because just one or two means I want three (or four, or five, or six!)!
When you think about how miserable it is just having one or two drinks, it's easier to just not have any