Why do I suddenly feel so Mature? As If I were 30,but Im 17.?

It sounds like you're moving on to another stage of your life. Everyone grows up at different rates and everyone grows through different phases, in different orders. What's important is that you never lose sight of who you are and who you want to be. Find the obsessions that make you love life - the obsessions that shape the way you view the world - and pursue them with nothing but uninhibited eagerness and curiosity.