The time between Christmas and New Year's is... strange.
There's such a huge build-up to Christmas, and then it's over in a day or two (or three, if - for instance - you have to travel between locations).
And there's also a lot of expectations leading up to New Year's Eve. Everyone tries to figure out how to spend the Eve, and to be sure that it's the best night possible.
The week between the two is kind of a slump, right in the middle of a peak.
I guess you could kind of look at it as New Year's being a way to "taper down" from the excitement of Christmas, but at the same time the week in the middle is kind of just weird.
You have to go back to work, but can't get anything done.
You have to try to eat well, but you're surrounded by bad-for-you leftovers.
You think you can get back to your "normal life," but you have another couple of festive days in front of you.
It's... well... odd.