There are some days where it is "OK" to relax and take it easy and skip your training.. I would say Christmas is one of those where you don't have to be completely anal and stick to everything 100%.. missing your Christmas workout or delaying it to saturday really isn't going to hurt anything.
Sometimes we all need to take a step back and look around us and find what is really important. For me it's spending time with my family and my fiance. Hell, we're even bringing our dogs along to my parents house for christmas. I'll be enjoying good company, good food, and some good television for the entire day. Training and diet won't enter my thoughts once throughout the day.
Were I single with no family, I would probably hit the gym were it open.