Great thread!
I also tend to leave up white lights and snow/winter theme items through at least January - helps keep that cozy feel, ya know?
And candles, have to leave out the candles!
Perhaps think about what you want your post-Christmas soundtrack to be - make a playlist of favorites that you know will make you smile. I usually listen to Christmas music while taking down/putting away all the decor but after that I am ready for a change!
I also look forward to "playing" with any new items I've received for Christmas, watching any new DVDs, reading new books, etc.
DS's birthday is Feb 5th so THAT is my personal project once the holidays are over!
Volunteer work is another idea - I'm sure the help various agencies receive drops off sharply just after the holidays. Whether it's a donation to the food bank or of your time - nothing pulls one out of the blues like helping others, IMHO in any case!
You could also plan ahead a treat for yourself - a massage, or pedicure, or time to sit in a coffee shop and write in a journal, whatever floats your boat that you don't get to do often or just don't have TIME to do during the holiday season.
Perhaps plan for a simple family event/outing post holidays? For those that can't afford an actual trip as mentioned - which would be awesome of course! A movie night at home? A game night (playing new video games received for Christmas) + snacks? A trip to a local museum? Or go out to the movies? If planned and budgeted for now it might be more likely to happen...
Or what about photo albums/scrapbooking the holiday memories? Plan time to get photos ordered and then insert them into a simple album or go all out and do a Christmas scrapbook.
Do some basic planning now for meals - are there healthier, simpler meal options that you'll be happy to have following the richer meals we'll all have been eating for a few months?
For those that like to garden, January is a GREAT time to start looking at catalogs and dreaming of what you want to grow come spring. Really dedicated folks can start seeds indoors around March so that is something to look ahead to and prep for.
It really helps me to visualize all those types of details, SEEING how I want things to be, then making lists and plugging things into my calendar to hopefully actually create that vision, at least as much as possible.