Christmas is the season for eating. And since it is kinda impractical to be denying oneself, why not use heat to burn the extra calories off?
Exercise, no matter how little, no matter when you do it, will always burn calories. You can just make sure to keep to your routine so you won't feel so guilty about all the dainty desserts you're sampling. Also, squeeze in some more activity to your day. Take the stairs. Walk part of the way to your destination. Do some leg raises. Stretch. Any activity that gets your body temperature a little higher will count. And yes, kissing and getting all giddy with excitement helps too.
Then, add heat to what you eat too, as these are natural fat burners. Make sure to include a bite or two of something that's more spicy than your usual fare. It may even help you eat less. Just don't binge on anything creamy after to take the edge off the spice.