Thanks everyone for your replies. I made it 3 and a half days. Last night I started shaking really bad... alcohol withdrawal, perhaps? Does that even happen? I don't know but I couldn't handle it and I had a beer. Dammit. The shaking stopped and then I just felt like a loser for drinking the beer so I poured out what was left. I decided to take it as a lesson for next time: letting myself down and the shame I felt for drinking overpowered the desire to finish that beer. A partial victory? Perhaps a complete defeat with a nice spin on it?
I'm tired of lying to my friends, and really tired of having to apologize to them. They let me off the hook pretty easily: "It's cool, you were drunk." I would be getting pissed off with me, if I were them. Honestly, how many times does "Sorry, I was sloshed," excuse your behavior? Not nearly as many times as I've used it.