Growing up as a Witness I can't say I ever felt that I was missing out on birthdays/Christmas/saluting the flag(who would want to do that is beyond me!) etc. But I guess that's kudos to my parents, however misguided they were religiously, they managed to give me and my brothers a great childhood.
I still couldn't care less about my birthday although my partner and friends do I've managed to invert tradition and on my birthday I arrange a surprise for them. This year they're going on a mystery trip, last year they were taken for a midnight walk through a forest illuminated as an art installation and had no clue where they were going until we got there. It's fun and I'm happy to do it any day of the year.