Preparing for my Christmas FEAST!!!

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Ok so Christmas is only 12 more sleeps and i'm well within my healthy BMI range. Problem is I have been eating really healthy for quite a while now and am wondering how Im going to cope with all the crap I plan to eat on christmas day.
Any hints on how to help me handle the huge amounts of bad sugary food i plan to take on without causing a sugar rush which will inevitably follow with an afternoon nap as i come plummeting back down.
Please don't say it cant be done.