Birthday woes...please help?

I’m 25 today...I'm not happy about it. A good friend of mine is coming from out of town to celebrate...it's her birthday too - we're b-day twins. She wants to party and I want to hide in my room all day. I hate the fact that I'll be 25 and my life is not where I want to be professionally or personally. I really thought I would have a family by the age of 25 but it doesn’t look like I’m going to meet a suitable man anytime soon. I don’t want to be a sour g when my friend comes to town. My question is: what can I do to pretend that I’m happy so that I don’t rain on everyone else’s parade?