When was your childhood over? Do you agree with the concept of adolescence, or did you go from being a child to being an adult?
To my mind, the transition between childhood and adulthood is one of scope. A child only interacts with her world on a local level; family, friends, people at school.
An adult realises that there is a larger world. One of the key realisations that turns a child into an adult is that there is evil in the world; that life, everywhere, basically sucks. This is partly why teenagers are so moody; they are dealing with the sudden realisation that the light at the end of the tunnel is a train.
There are horrible things and horrible people, and, furthermore, there's no present authority to whom one can appeal to for protection. Being an adult means knowing that one has to take responsibility for one's own actions, and one's own problems. An adult can no longer rely on his parents for rescuing.
Even children who have awful lives, as children, are generally focused on thier own suffering. As they get older, they become aware of the suffering (or lack thereof) in those around them, and begin to react to their larger environment.