Do not restrict yourself over the holidays
Restricting calories over the holidays is never a good idea for a multitude of reasons. Let me start by saying that a diet break for a couple weeks can actually accelerate fat loss once you return to a calorie restricted diet. The reason for this is that when a person diets for a number of weeks in a row for a long period of time, a hormone called leptin (king of all fat burning hormones in the body) is depleted. By taking a break from calorie restriction, leptin is restored.
People need to have a balance between fitness and lifestyle. You will be surrounded by great foods to feast on, no person wants to miss out on good food and good opportunity. When people try to restrict themselves over the holiday season, often times this leads to guilt eating and binging. The person will feel like they miss out on the opportunity and will try to make up for it by over eating.
There is nothing wrong with enjoying yourself for a bit of time. When calories are higher, it makes gaining strength and muscle SO MUCH EASIER because there is more calories to work with. Strength will skyrocket so winter time is the best time to make true progress in the gym.
Enjoy life to the fullest while still maintaining your physique and health. Balance is key.