The Origen quote is found in the new kids book "listening to the great teacher" or something like that. It came out a few years ago.
Anyway, you can look the quote up on the catholic encyclopedia to find out the actual context. It has to do with celebrating our life on earth instead of celebrating the day of our death and we inherit our heavenly reward. It doesn't have to do with christians not celebrating their birthdays due to paganism.
If I'm mistaken on this please post it to this thread.