I've started to think that you can attain maturity through two channels: 1) experience and 2) learning indirectly through media like books, internet discussions, etc.
People who are thoughtful and empathetic but shy and/or anti-social tend to pick up maturity through #2. I think I fall into this category. Learning indirectly (method #2) is efficient. You can learn a lot very quickly. The problem is that it's very hard to develop emotional resilience by learning about other people's experiences. You can read about what it's like to suffer a divorce or a life-threatening illness, but that can only prepare you so much.
People like me can be mature and seem exceptionally mature for our age, but when we run into a difficult situation, then our lack of experience is exposed and basically, we're screwed.
However, I'm not recommending that people should stop reading and learning about other people's experiences (method #2). Direct personal experience is great, but it is very limited. There simply isn't time to live in different places, travel to every country of the world, try out different careers, etc. I would be wary of people who claim that experience is king and that reading is a waste of time.
Simply put, we need both experience and learning to become a wise, mature person.