How fast do we grow?

Seems it was only yesterday that I was watching "The men in black" and wondering who the black guy was , so my sister filled me in. And now today as I was wandering through the TV , some song caught my attention , it was something like this : " I woud never say never , I will fight , I will fight till forever ...". I recognized Justin Bieber , I knew him from that other song I'd heard , but I wasn't sure about the younger kid.
I got all curious and googled the song , it said that the other singer was named Jaden Smith. Smith?.. I suddenly recalled that I've seen the little kid on Oprah with his mom and dad , Will and Jaden Smith. So it was their child I was seeing after all , now a teenager. I was suddenly feeling a little old , if he was 13 now , how old would that make me? Ugh , I'm still used to the feeling that I'm 15 , but that's sure about to change. I'm about to turn 20 in 2 months , but somethings wrong. I mean I'm all grown up mentally and physically , it's just that I've never looked at myself that way , like an adult. Soon I will be going to work instead of college , no one would be asking me anything childlike , instead they'll be intereseted in my points of view. I guess I could manage , but I would never be the person I am now , I will this boring adult who thinks about serious stuff like money , apartments , the bills , the kids. Oh my god the kids! How can I be thinking about the kids when I'm one myself. I seriously don't wanno grow up right now , like if my life was a movie and some one had the remote , I would beg for a pause now.
Everbody excepts the grown up to be so different from the young , what if I don't want that? What if I wanno be my own version of adult , the one who's mostly a giant kid.
But at least I'm sure about one thing and that's I will some day change my mind , and will be the day for a new "play" button on the remote.