MLAN613 ..... this reply is in two parts.
I was having some difficulty finding my "Christmas spirit" until I remembered that Christmas is a celebration of the fact that God, wanting to reconcile mankind to Himself, asked His Son, Jesus to come to earth & minister to us by becoming a human who would teach us how to have fellowship with the Father. He died and was resurrected, giving His life for mine. Jesus did for us what we could never have done for ourselves. Because of this obedient, loving sacrifice, I have NEW life, here and in the hereafter. That means that right here & now, I can daily experience grace, strength, and peace.
If you're not a Christian, then what I would say to you (beyond the ideas offered so far) is to turn on some Christmas music and sing along! This is bound to "warm" you up inside. The other posters had some great ideas too. Decorating (even just a little bit inside your dwelling) or doing something nice for others can be of help. You'll find that if you just do a few simple things, you will receive more than what you put in.