Step 1, eat enough protein.
Step 2, continue with your work outs.
Thats it. Despite all the ranting, raving, hand wringing and self pity that goes around this time of year, my advice to you is have a good time. Yup, you heard me; eat too much, drink too much, stay out too late, dance with your wife, flirt with the secretarty, have a good time. If you do nothing else but make sure you eat a healthy serving of protein at every holiday event you attend, and keep with your twice weekly workouts, you'll be fine come January 2. Maybe you'll have gained a pound or two, maybe not. As long as you keep lifting, at least part of it will be muscle. Come the frist of the year when things calm down, and you retrun to a normal eating pattern, and keep with the lifting, any extra fat will take care of itself with no extra effort from you. Plus you'll have the bonus of having added a bit of muscle in the process. If for some reason you have to go somewhere that may not have much protein, or you just want to keeep things in check, chug down a protien shake before you leave home. Water, ice and protein powder in a blender, gulp, go, party on dude!.