Don't throw in the towel! You've done so much amazing work so far. One beer (yes, you shouldn't have had it, yes, having it made your life a little more challenging in the short-term) does not obviate the work you've done and the progress you've made! Don't let yourself use the slip as a starting point for a shame spiral. I think that what you've done so far is amazing, and I'm sure you have the strength to pick yourself up and keep on pushing through.