Christmas dinner will NOT make you fat. One dinner cannot put 10 pounds on your body. Eating cookies and giant meals almost daily between Christmas and New Year's, and drinking alcohol will. 10 pounds, I'm not so sure. The extra salt will add water more than anything, and sure, you will most likely pack on a few pounds.
Here is a word of advice....
Who cares. Enjoy. Have fun.
Be more concerned about what you eat between New Year's and NEXT Christmas. The daily good habits you establish all the time will do more for you throughout the year than the rules you press on yourself during the most tempting time of the year. Trust me, although you may take a break and get a little off track during the holidays, it won't be enough to ruin you forever. Just start again in January. We all deserve to eat drink and be merry every once in a while.
Dieting is the worst thing you can do in January. Make changes to your habits, but remember not to do it all at once. This will set you up for failure as you rebel against yourself. Instead of going all out on your list, I have one suggestion for you.
Pick one change a month
Jan Move more. take the stairs at work. Dance with your kids.
Feb Drink water every day. Cut out juice and Pop.
Mar eat a fruit or veggie with EVERY meal.
If you have trouble making changes doing things one step at a time can help. Of course my ultimate suggestion is to get out the door for a 'walk' 3x a week. 10 mins out, turn around, come back. I don't care what the weather is...bundle up. You will be back before the start of your next show, will de stress and sleep better. It will also motivate you to start the changes listed above.
Happy running! ( or getting off the couch )