I'll let you in on a little secret.
No one grows up. Everyone has the same sense of joy and fear and ego they have had since they were first conscious of themselves. People have different demands made of them in life, some by themselves, some by circumstance and some by expectation but the idea that because you're doing something with your life someone else isn't doing doesn't mean you aren't 'growing up.' I'm not going to stop doing silly voices to my husband to make him laugh just because I'm 30.
Hmmm I can't say I disagree but I do recall you not approving of that trait of me.