I'm convinced it's all in the head... we KNOW deep down that most of us will have some treats on Christmas Day, and then it becomes more difficult I find in the days leading up to it. I'm exactly the same just before leaving on holidays!
"control" is the key... try to take back control of that resistance muscle cos, as we've said, plenty of damage can be done in the 9 days remaining before Christmas!
If all else is failing and you're still feeling deprived and picky, another trick I use is to say that YES I will/can have some of [whatever]. On the 25th. But right now I'll have [chicken/eggs boo hoo!]. Maybe try it... pushing off the inevitable somehow.
I also recommend planning 26th PP menu... so as not to get carried away IF Christmas "happens"!