I have a freind who's Father died suddenly in his 40's on Christmas Day.
He didn't celebrate Christmas for almost 20 years and only started again when he got married and had children. You can tell its still a painful time for him however slowly he is moving on.
It takes a while.
My Grandpa passed during Christmas when I was 8, and my Grandma was in such a deep depression that we didn't have Christmas until I was grown and moved out. It takes a while...