Many humans are quite sensitive when it comes to aging, which of course is a natural occurence in life. They try everything within their own power and the wonder of science and technology to defer the aging process as much as possible. They also stop celebrating birthdays so others will not have the chance to know their ages. I think it's strangely funny.
For many, birthday is a commemoration of another year in one's life. But I have a different concept. I think birthday is a reminder that another year has past and taken away from one's life. It's like the mathematical formula x-12, where 12 is my age and x is the number of years i will live. The mystery number x is something that many humans are apprehensive about because no one knows what the number is.
The way I see it, since no one knows what x is, it is totally useless to worry about it. It is more important to do your best everyday. When the time comes to celebrate the passing of another year, you can at least be proud to say that it was another year well spent and well lived.