Well done on starting again on the road to sobriety, rather than just brushing what happened off and carrying on as you were. It isn't the easy choice, but I admire you for it.
Quick question, given how concerned you are about it, would it be a crazy idea to just pull a sickie and stay home tomorrow? Nobody would think you're not really ill if it means missing the Christmas bash everyone is looking forward to. Just seems a big test of your new resolve to put yourself in that situation so soon after deciding to quit.