Stop celebrating the Holidays! Seriously. Give away the rest of the cookies, the entertaining should be settling down, as well as the huge Holiday dinners, complete with whipped cream desserts.
I feel that we only "think" we've gained a ton of weight. In reality, it's probably no more than 5 lbs, maximum.
This should drop off easily just by returning to our usual eating habits and getting back to work and being active.
If it makes you feel better to punish yourself for Holiday pigging out....just do about 20 minutes worth of some sort of exercise, every other day. Another trick that helps is to make certain you cut yourself off completely from any food or beverage at 6pm....PERIOD....every single day for at least 4 months... Good luck!