So I started writing a book in response to the early comments in your post, then I took a few deep breaths, and continued through the rest of your post. When I got to the end, I realized that my previous response was pointless :)
Growing up is not really all about the age, it's more about what you have gone through in life.
This is absolutely true. I feel like you're describing the difference between being Smart and being Wise. You can teach someone to be smart with enough time and effort. You can never teach someone to be wise.
Wisdom takes reflection on your surroundings and situations and understanding of cause and effect. Being smart simply means that you understand a concept.
It's why you see some young people who have gone through various difficult and sometimes traumatic experiences are so wise to the happenings of the world. They have seen death. They have seen birth. They have seen true love. They have seen pure determination. They have seen extreme hate and evil. And they have reflected and learned about what it takes to survive and how to experience a happy life, regardless of your circumstances.
Oops, I think I wrote another book.. :)
Wise words.
You can always write another book!