This is why I made up the Heathen Holiday idea (actually, I've called it by several names over the past few years, but I think I'll stick with this one--it has a nice ring to it.) Being an Atheist or Spiritualist shouldn't preclude you from having a special time of year to spend with family, to eat and drink too much, and to give presents.
I like to choose something to fangirl over, making it something of a nerdish holiday, if you will. Last year it was the Hobbit movies, and reading the entire Mortal Instruments series in a week. This year I thought I'd get the Avengers movies, but my plans have gone a little off course. The beauty of having a Heathen Holiday, however, means that you can hold it whenever you wish.
Whatever you do for the end of the year, whether it's Christmas or not, I wish you a great time, surrounded by people you love. Be safe, be something like good, and enjoy :)