I figured a very simple answer. Might sound a little complicated when reading, but to me, that's nothing.
If it is true that you feel that when you were you younger, you used to really enjoy Christmas, compared to now, I have a reason why.
I call it 'expectation', coinciding with the following fact.
As you become older, as I have noticed in the last couple of years, the world is much bigger than you thought. There *is* something after school - something very big. Your life. Money, family, responsibility.
I think that as more becomes expected of us, we expect more out of things (like money from people as a cheeky example). Now if we suggest that if you are doing the same things you used to do as a kid (which may be your answer to finding your 'spirit' of Christmas anyway), then it is natural to feel that you don't feel 'in-touch' with Christmas.
So my answer to doing the best you can to enjoy Christmas is to integrate it as much as you can into the seasonal timing. Doing all the usual things - buying presents, setting up the tree, playing games, visiting family, giving cards and presents and receiving them, thinking about those less fortunate, singing festive songs, maybe even visiting church - generally thinking about the reason and purpose of Christmas.
I mean, don't get me wrong, I'm sure you've all probably figured that you're just happy as you are, I'm just writing this blog for a friend who said he didn't feel the spirit. And if he doesn't understand all this, well, stuff him :P