Surely it's not just because the silly season assures guilt-free indulgence.
I think moreover it's because Christmas is a triumph of tone; that rare juncture where we look neither back nor forward. It's a time of presence.
We care only that the kids are happy and that something that once either clucked, mooed, baaed, roared or squealed is spinning slowly on the rotisserie.
In contrast, the second week in January marks a return to the aspirations of temperance, moderation, graft, common sense, early nights, self-improvement and working whatever hours you need to afford said protein for next year's rotisserie.
We treasure the festive season so dearly because we know there's a steep descent just over the hill.
Needless to say, now's an extremely tough time of year to stay positive.
But, as I heard someone say recently, rather than cry because it's over, smile because it happened.