(I'm 32)
The first thing I came to terms with is that 30 isn't "old". I'm looking at 40 up ahead, and that isn't "old" either.
My parents both turned 60 recently, and even though they're greying slightly, I honestly don't consider them to be "old". My dad plays drums in a band, they get booked to play at all kinds of parties locally. He built a practice room in their house, complete with separate mixing booth and recording facilities. When they go play, they lug all the gear themselves and set up a stage and everything.
My mom does realistic movie character doll heads for Barbie-size dolls, sews clothes for them and builds complete dioramas.
My uncle, who's in his mid-60s and just retired earlier this year sails kayaks and has built both a beautiful wooden kayak as a birthday present for my aunt, and he's making another for himself. He's also still active in the regional dog training club, for over 30 years now.
You get older, but you only get old if you give up and stop doing things you like, if you get overly conservative and start just complaining about everything, instead of going out and doing things.
Dude, you're 24! Life is just starting! Get out there and enjoy it! :-)