Grow up

At what point do children actually become adults? When, instead of being the kids on the street asking for candy do they become the parents giving it out? I have wondered about the question for awhile and the only conclusion I could come up with is that they simply do it out of tradition. I have always heard my collective teachers voices constantly repeating "act your age" "act your age" and I honestly wonder if they know the meaning of the phrase. Couldn't they see that we all were acting our age? Couldn't they understand that we never really grow up? Now I understand that we do mature emotionally and physically but that is a product of nature not of ourselves. I have and will always act my age and it is foolish to assume that being a certain number of years old automatically transforms you into a certain emotional configuration.  I have wanted to vent this for a long time because of the absurdity of the phrase and I hope this stops all zero people who read this from using it.