Nat, you have a very small amount to lose, and therefore, much more chance of gaining the whole amount back with a little slipup. If you are serious about making this a change for life, try to keep away from beer, period. It has the highest GI of any other food, even sugar!
Try having red wine instead...easier to stick to one glass, and it doesn't cause problems. Try making a dish to take with that is SBD safe, and bring along lots of fresh veggies and dip. You can do this!