It's funny because when you're a child, you believe you

 It's funny because when you're a child, you believe you can be anything you want to be,
go wherever you want to go.
There's no limit to what you can dream.
You expect the unexpected, you believe in magic, in faitytales, & in possibilities.
Then you grow older & that innocence is shattered & somewhere along the way the reality of life gets in the way & you're hit by the realization that you can't be all you wanted to be,
you just might have to settle for a bit less.
Or perhaps a variation of what you wanted.