You are not automatically an adult when you hit puberty or turn 18. Some people grow physically but still have a long way to go before they are emotionally ready to be adults. To stop being called childish or immature, you would have to do things like being happy for other people.
CuriousMob.com looks at the qualities you need before you can call yourself an adult.
10. Having control of your own emotions
A mature person wouldn’t be quick to get angry at someone else for something they did. Instead, they would be quick to keep their emotions in check. If you are mature, you will be less likely to let your emotions get the best of you and act in a bad way.