I don't remember Christmases (or much else, really) from when I was a kid, but as I grew up, Christmas was always a time of sadness for me. I'm not sure why, really, there was never any great trauma in my life as a child, nothing horrible happened to me or anyone I loved around Christmas time. Yet I continued to get melancholy around the holidays. I'd listen to songs like "The River" and just get all angst-y and sad.
Since having kids, though, I have rediscovered the joy of the season. Since we are not a religious family, our Christmas celebrations lean more towards the hedonistic Santa-and-reindeer centered sort, but we also focus on the love we have for each other, and for our family and friends, so I don't make any apologies for our less than devout interpretation of the season.
This year, especially, I am truly enjoying watching my children light up when they encounter each aspect of the holidays. Light displays, neighborhood decorations, Santa at the mall, etc. Each new thing (whether they've seen it every year or not) causes a joy in them that is just beautiful to watch.