I'm just shy of 31 and I have to say when I look back 23-24 was the peak of feeling like I was "too old" to accomplish anything meaningful.
I think one of the hardest things for me to see at 24 was just how non-linear and strange life is, and likewise how truly meaningless it is to try to establish a useful system of measurement and comparison between individuals.
For what life advice from a stranger on HN is worth: Get out of the game of comparing yourself to others as fast as you can. Focus on what you think is interesting, and also take a few moments now and again to really appreciate the wonder that is life. Aside from being happier, you'll most likely accomplish more if you don't spend energy casting yourself in the shadows of others.
But, y'know, sometimes you still want some perspective on how you're doing :)
[1] for instance my mum and grandparents keep throwing people my age who are "starting real adult lives already" at my face, whereas I'm just playing around with freelancing instead of looking for a job job
[1] http://mathoverflow.net/questions/3591/mathematicians-who-we...
I mean, do you know that Turing was just 24 when he published the Turing Machine paper? And a mathematician whose name I can't remember right now, practically revolutionized set theory at ~22.
There's a bunch of other examples like that.
Hell, I have friends my age who've published more than one academic paper. Some of them highly acclaimed (enough so to present them at MIT)
Comparing to normal every once in a while is definitely the only way to keep one's sanity and allow oneself to get some sleep now and anon. OP has no idea what they're talking about.