Christian or not, Christmas is nigh-escapable this time of year in America, so just go with me on this one…
Choose one aspect of Christmas you feel is absolutely essential. Now, write a story about set in the Christmas Future in which that one aspect is no longer present. Maybe tales of Santa Claus have been outlawed by the government. Perhaps gift-giving has gone the way of the dodo. Or maybe global warming has eliminated snow. You might choose to not even acknowledge the missing aspect in your story at all, finding a way to work around it completely. Give this exercise fifteen minutes of your time, thirty if you treat yourself to egg nog during the holidays.
Write it up and see what happens.