It's okay to take your foot off the gas and relax a little over Christmas. If you're performing over the festive season you're still going to be active, if you're not performing you can allow yourself a break. Drop in classes tend to tail off for a couple of weeks so use it as time to go to the gym, exercise outside or do something different. Your body will thank you for the change of pace.
With this period being one of the busiest for most performers, it's important that if you get a chance to relax and see your family and friends that you make the most of it. Don't overdo the work, let yourself unwind for a day or two, don't worry too much about the amount of food or alcohol consumed - the damage of a day is negligible and the damage of a few days will be cancelled out in no time. When you've been going flat out since September there's always a risk of running yourself down or burning out. There's no harm in taking some time out and enjoying yourself and you'll be in a better state to continue with the rest of the season.
If you are performing over the festive period still take time to enjoy your day off. If you're on tour, make a point of having a day that breaks the grind on Christmas, even if you can't make it back home. It's important both mentally and physically to feel you're not being worn down; even just for a day, a change of pace will make the rest of the run easier.