Maybe if you go ahead and just DO some of the usual Christmas time activities, it will eventually help you FEEL the Christmas spirit. Put on some lovely carols, do some shopping and wrapping, make some Christmas cookies, participate in a giving tree and purchase and wrap gifts for small children in need, help at soup kitchen or food pantry, drink a little egg nog early, watch a favorite Christmas DVD, drive around and enjoy the lights others have already put up, etc.
I have struggled in the past with this issue and a combination of doing the normal things I usually do and doing something nice for others helped.
Also you could add some special prayers, fasting or giving that would help the season feel more meaningful to you.
:hug1: