We can complicate things, always. We can analyze the minute details of psychology, try to cut corners and play tricks on ourselves to stay on track - but sometimes, these things make us feel like we're depriving ourselves and then we rebel against what we didn't necessarily even know we were doing. Staying on track is pretty simple.
Do you want to stay or get into a body that you feel great in and are proud of?
Do you want to have more energy and laughter over the holidays? Or do you want to be lethargic and feel like you've been hit by a bus after?
There's a difference between feeling beaten down, and relaxing. That post-meal nap is great, always. But if you've overindulged you'll have a very hard time prying your eyes back open in time for the next activity.
Stay consistent and active. In my opinion, going longer than 3 days without some heart-pumping activity is too long in the interest of energy and health. Taking a full week off is probably a really bad idea. I personally take about 2x full weeks off / year (not lumped together) because in the big picture it's part of my regime and good for my body when I return to training. But, if you've had quite a few days off in a row already this year, it would be great to keep yourself moving over the holidays.
Sneak in activity. Even just moving around the house, dancing, chasing kids, tossing toddlers in the air (this is a personal fave - do it carefully ;) ) all adds up in the end. Go for a walk with family on Christmas day after a big breakfast.
Watch the endless platters of nuts and snacks - you can easily consume a meals' worth of food with a few minutes of snacking amid conversation. A small handful of nuts is 250-300 calories usually. A few days of added meals and you'll be feeling mighty heavy and uncomfortable for NYE.
The simplest part is, you simply have to want it. You have to want to keep moving forward and feeling better and better. Setting yourself back means creating more work for yourself later. It means risking discomfort and discouragement, which slows everything down for longer than we'd like.
You can still have your favourite things, just keep the portions controlled and focus on laughing more and munching less.
That alone, works wonders.