When you don't know what's the problem...

So this is the situation, Currently I am 21 years old. From past few days I am having a strong feeling of doing something good with my life.
I wanted to do this and that. I wanted to learn this that. Life was always easy for me. All of my friends are having married one by one. And now we only talk about their family issues. A strange feeling that i am ageing. Time running fast. Is I am mature or not. I wanted to achieve my goal and those dreams. These all things just make me sad. When we don't know where to start and when to start or even what to start. This is life; we born, we do something and we die. That something decides our life worthy or not?
I don't know why I am sad but one thing is true that i just wanted to have this feeling always. You know, every feelings just lost and you have new feeling the next day.
This feeling that i am having currently. This feeling, because of that i am writing these lines having no meaning. I like this feeling. This feeling motivates me to dream, to face problem, to achieve target, to just make my life worthy living. I have got my inspiration and that me itself.