I have this friend, let's call him 'Bob', and he claims to have the heart of a child. What he means, is that he likes to have fun, laugh a lot, and be care-free.
Yes, these are all qualities that children possess, but Bob isn't child-like. He's childish. He is immature, laughs at other people's expense, plays cruel jokes, teases and ridicules others, sulks when he doesn't get his way, forgets to factor in other people's feelings, and is highly motivated by praise and winning.
I've noticed as I've gotten older, that there are two types of child-like people - those that take part in innocent fun like building sand castles and getting dirty, and those that, like Bob, act like a child.
I don't think anyone consciously makes the choice to be one or the other, though. At least, not until someone draws their attention to it.
So I'm drawing your attention to it now.
There is a difference between playing around and being little, like children, and acting like a child who doesn't know any better yet because they have yet to learn a few key life lessons.
Acting like a child when you are an adult doesn't get you very far, or leave you with many friends or opportunities. There is no need to sulk, there is no need to be mean.
Playing at being a kid, like staying up all night to have a movie marathon or playing dress up with all your clothes, may not get to somewhere, but it definitely helps with your mindset. These a positive things to relish in occasionally. You live in the adult world because you are an adult, but it is okay - in fact, I would recommend it - to play at being a kid sometimes.
Doing kid-things makes you smile, makes you laugh, so make sure to include them in your weekly life. Just don't turn into a child, who hasn't learnt their valid lessons yet.