Cheer up man, birthdays are great. Don't concentrate on the number and all that bollocks, have a good look around you and concentrate on the fact that you're alive and live in a pretty **** spectacular (if sometimes shitty) world.
This after all, really is it. Once you're gone it's game over, so try and enjoy it and don't get dragged down by wishing it was the past and a few oncoming grey hairs.
(ps it's mine next Wednesday and i'll be 44 - so 30 is **** all)