I wonder what you decided to do? Sorry this is posted too late for your party but one way I can stay healthy at a gathering is to keep a glass of water in my hand at all times. If I've got that it's hard to drink or eat other things. I also try to spend time talking to my friends as far from the food as possible.
Those are some options if you don't feel strong. Regardless - don't beat yourself up. Get up the next morning and get back in the saddle. No one is perfect, and one night of imperfection should never cause you to want to give up.