Generally speaking a birthday should be the day when one is happy with the cards & gifts from friends, party or just the prospect and the hope for the future. IT might be the reason I always feel blue on 9th Feb, or the reason might be just that I don't have my own family or the current miserable job situation. Single women tend to feel loneliness and serious regret for their lives sometimes even though they usually enjoy their solitude and freedom, and for me the 9th Feb - my birthday is always a such day.
I don't mean I have no friends who celebrates my birthday. Some send me cards with kind words or gifts every year, and some ask me to eat out together.
Still generally I have felt really blue on this day for years, feel very aggressive and everything seems to me so worthless and meaningless. And the fact that I feel blue on my own birthday depresses me more. I sometimes analyze my feeling, and I know this is not the envy of other "happier" people. But part of my depression comes from the human relations and similar problems, I have never been good at the social contacts. And I fancy the life in a little cottage in the countryside with no neighbours around me, no chatting, no noise... (sigh).