I was raised a Dub, and what I found was that when I tried to celebrate birthdays or holidays it felt as foreign to me as celebrating Ramadan or Bon-Odori would feel to a life-long catholic; it simply "doesn't compute." The reason for this, I've concluded, is because there is no established emotional base in me for these events/activities. There is no emotional context.
I can relate to that. There are some aspects of some holidays I like and enjoy, but other aspects I can't get excited about. Having been raised without ever celebrating these things leaves me without an emotional attachment to the celebrations or events.
I tend to ignore all the religious holidays. Xmas doesn't do much for me when it come to trees, lights, decorations or the story of baby Jesus, but I love the xmas parties and the holiday cheer that comes around an otherwise gloomy time of year.
I always secretly liked Halloween as a kid so now I enjoy it without shame or guilt and enjoy going to parties dressed up in a costume.
B-days I don't care much about. I'm at an age that each passing b-day just reminds me that I'm getting old. Knowing that and realizing that there is no "paradise earth" in my lifetime doesn't really give me much to celebrate.
It's come down to me taking what I like from certain holidays and leaving the rest.
It's like moving to a foreign land. When you move there, you may not have any clue as to local customs and traditions but as time goes by you tend to adapt to them and while you may never fully appreciate it as the locals do, you learn to appreciate it enough to enjoy it with them and to respect their ways.