When Life Gets Awkward

I remember my ninth birthday, for some reason I was really into my birthday that year. More then I recall ever being. I stood in front of my big lemon cake, my face aglow in the light of ten candles smiling so big as everyone sang happy birthday to me.

Fast forward ten years, I was mortified that my parents sang to me on my birthday in front of strangers! I didn't want the attention, I didn't want to be sung to.
I remember thinking, when the hell did that happen?
When do you start hating "Happy Birthday" and why? Is it because we are getting older, or less in need of a "moment"?

In a related question, at what age do we stop referring to our age in halves? You almost never hear of someone saying "Well, I really came into myself now that I am 36 and a half" or "I had my first lesbian experience at 25 and a half".
Almost never.