How do you know who you are?

I have had three years of my life ruined by guys.. Dont really want to go into all the details it would take all day.
So I was wondering how did you find out who you are and what makes you, you? Do you just figure it out as time passes or is there something you did to find out who you are and what makes you tick? How did you get to the person you are today? What makes you yourself?
What do you suggest I do to find out the person I am and the person I should be?
I am only 16 and I would like to know who I am before I graduate..
Any suggestions would be appreciated.