By the time you get into your fifties you have more answers, less problems, some entrenched bad habits that are nearly impossible to break, a whole lot of dreams that you know you'll never achieve, someone who looks like your parent looking back at you in the mirror, and the search for sex is no longer an overarching need - but inside you'll still feel young.
At thirty you probably feel as old as you'll ever feel. You always feel young inside but at thirty the world stops looking new. That soon passes though once you realise that you haven't been paying close enough attention. The world will always be new and that you'll always feel young even if you live to be a hundred.
Damn, that was beautiful.