This happens for at different ages for different people, and for particular individual reasons. It is a kind of dissociation: a "part" of you becomes emotionall

This happens for at different ages for different people, and for particular individual reasons. It is a kind of dissociation: a "part" of you becomes emotionally stuck in the past, either because of trauma, or not making peace with the past, or being unable to make continuous sense of your identity relative to your life. Something like that. The modern world is full of 50+ year olds pretending to be teenagers because there are no other coherent scripts to identify with after that point. I expect for a lot of people, the "break" happens when they have to join the workforce and give up on whatever ideals they formerly dreamed of.