Not really much actually. From my experience with many of my friends that are 30+, I have basically the same life experiences. Your point is moot unless you can provide examples. Career? Kids? School? All of those can be achieved in your 20s and not be crappy either. By the way, the transition from 10 to 20 is way more drastic than 20 to 30. If you say otherwise you are not very intelligent. Puberty alone proves my point. You used a shitty example.