Others have felt your pain.

I used to date a Jewish girl, and she found she actually really liked Christmas, since she had never had a chance to celebrate before we were dating. Whether or not Christmas is enjoyable really depends on the people whom you're celebrating with. I happen to have a big family who are all really close and who all get along really well. I'm lucky in that regard, I guess. Even though we were all raised Christian, there's nothing remotely religious about our celebrations, and among our group, we now have a Jew, a Buddhist, a bunch-o-atheists...even a Catholic! We celebrate by drinking whiskey and playing team board games (Cards Against Humanity was last year's game, and I think my aunt kind of peed herself, which is a great way to enjoy the spirit).

So anyway, my point is that "happiest time of the year" is a silly phrase, but if you strip away the historical and religious context and just view Christmas as a time when all your family, many of whom are now spread around the country, can get together for a few days and have a few drinks and a few laughs, then it's pretty damn awesome. Christians stole Christmas from the pagans in the first place; we should all steal it back!