"歳を取っても大人になっていない"

Simplified Meaning:

As people get older, they often change how they look and sometimes how they think or act. But, for some, their playful spirit and joyful attitude stay the same, no matter how many birthdays they’ve celebrated. For example, think of someone like your grandfather, who might have grey hair and wrinkles but still loves playing video games or telling funny jokes just like a kid. This idea shows that while time passes and we grow in age, our enjoyment of life, curiosity, and sense of fun can remain youthful. You can use this mindset to remind yourself that it’s important to keep that part of you alive, staying curious, playful, and enjoying the small things, regardless of how old you become. Don’t let the serious parts of growing up take away your ability to have fun and be happy.