Mature at age, but childish in attitude?

Erm, I'm currently 19 for now(going to be 20 on October), but there's something's still puzzling me(yes, myself). I wonder even my looks is pretty mature, but I'm still have my childish self, like always sulky whenever my friends tease me, have a childlike voice(in a few times when I'm disagreeing on something) and rather quite(?) playful.

Aww come on, we're not THAT childish, okay? x3

Sometimes it's fun to be a kid, but someday I have to come over to adult(but I'm still want to retain my childlike personality at least, or maybe being a slight Kuudere or Dandere)

And some people mistaken me older than them :o

About me(again):

• I have a rather normal appearance
• I'm a goddamn ditz and clumsy
• Lazy but smart
• My blood type is universal( type O )
• Kuudere + Yangire= ummm.....
• Aiiro(deep blue) lover
• Animanga lover
• Expert in games(mostly online)
• And a really sensitive person *sniff*