The title is a butchered CS Lewis quote but I think you get the message. One of the things adolescents fear is looking childish, I think children themselves feel shame if someone accuses them of being acting like a child, despite being a child a quality of being young and something to be enjoyed. Not enjoying childhood is a complete waste and taking childhood from someone early is demonic.
What does it mean to be an adult? There are somethings that an adult can do, they can buy adult things like alcohol or monster drinks at a certain age but it is not the age that is important. Its the quality of their relationship with society. An adult is a person (literally a legal person) who can be trusted with potentially harmful materials, substances, actions and relationships to enjoy them responsibly and in a socially responsible way. The way we judge this is by age. I often wonder if people should take a personality test to be allowed to date, a genetic test to assert if they can handle beer etc etc but then my dystopia alarm goes off. We have to trust people.
I thought I would feel like an adult when I could do adult things without being supervised. I imagined that beer, a girlfriend and a job would make me an adult. I was wrong and these things were shallow opportunities to be an adult though rich and rewarding in themselves. Something was missing. These experiences were symbols or signals of my adult hood and I was wearing them like scout badged sewn onto my jumper. I thought about it long and hard one night in the university bar where I suddenly realised that I did not want another beer. What I actually wanted was a lemonade, a crisp, cold and refreshing glass of lemonade. Part of me recoiled and I imagined people looking escance at the adult man drinking a lemonade but then I thought that it was only pride talking and if I wanted something from my childhood why not get something from my childhood. In that moment a whole new world opened up for me. Now that I was an adult I could enjoy childish things.