One of my favorite sayings with regard to "controlled drinking" is, "Once you try to control it, you're already out of control."
My own personal method: I would save the stirrers/straws on the bar, so that I could keep track of the number of drinks. I knew four was the magic number...and, if I kept on after that, it was downhill all the way. But, I would still insist that the bartender leave the mixers...by the end of some nights, I had accumulated enough to play a game of Pick Up Sticks!!!