Hey, just remember depression passes, and you'll feel differently in a day or so. You may even wonder why you were so depressed to begin with. If it's any consolation, I never, ever celebrate my birthday, and take it as a blessing when the entire day goes by and no-one calls, no one writes, and no one even knows anything about it. I breathe a huge sigh of relief when the day is over, because it's the one thing I really want, that nobody even knows about it. In that way, my birthday is special, to me, and almost sacred. I love getting through the day without someone spouting some purile pap and blathering on about it.
When you're depressed, I think the first thing you should do is: Not do anything. Don't judge yourself, don't think about things, and above all, do NOT consider self-harm. Emotional cycles change all the time, so try to just look at this episode as having occurred in a not-so-good-cycle. Believe and have faith in something in your future.
Good luck friend.