You're old if you're old compared to your friends, and young if not, I think. (My friends range from 11 to 60+, and I'm nearly 29, so I get to feel young and old - and I spend my time either enviously wishing I was older in terms of experience and knowledge or younger in body).
[ZK] Make the most of it. Before you know it you'll be a miserable embittered Finalist, and then that's it. However, if you survive as a Finalist, you may have the option to become a Postgrad, which is best of all because you have less pressure, less work, more spare time and a real superiority complex. That's my experience anyway...
[Projoy] Having recently discussed with three of my closest mates (all of us are 40ish to 50ish) what we would do differently if we had our time over again, the answer was unanimous, unambiguous and immediate : shag more girls while we had the chance - by being (a) bolder, (b) unconcerned about rejection and (c) less fussy. (Substitute as necessary for your gender and sexual orientation) - That's the best advice our collective 200-odd years can come up with.