When Did We Lose Ourselves?

When did we lose ourselves?
When was it that we went from being bright eyed children without a care in the world to jaded teenagers?
Was there an exact moment?
I don't think there was I think it was a gradual change.
When did we start caring about what other kids thought about us? For me it was when kids learned how to be mean and exclude other people, mainly me.

I like to think I never lost myself. I'm still child like with the way I talk and act but really things that happened as a child are just gone. That feeling before Christmas or a birthday. Gone. The first feeling of a failure. Happened a while ago.
I guess it isn't even really losing yourself. It's really just growing up.