Who am I?

See, that's the line that you hear told in such a cliche manner in so many movies and books.  It's not a good line.  As a matter of fact, it's a horrible line, and no person in their right mind would say that to his or herself with sincere seriousness.  If a person did, then they need to learn to get a grip.

Who you are IS a real idea, though.  To understand who you are is a bit of a hard thing to do as you change and grow.  You go through experiences that make you seriously question who you are and what your meaning is in everything.  Your meaning in anything is actually meaningless, to be honest.  You're a byproduct of nothing and thus have no influence on anything in the universe.  If you feel like you mean something to anything other than people, then you're clearly arrogant and pretentious.  Life is meaningless, but it's relative, so in a way it has meaning as long as you make it meaningful to yourself.

Finding out who you are is a long-winded process.  It requires patience, time, and perseverance.  You can't have an epiphany and then just immediately figure out that you are this person with these likes, dislikes, and moral feelings; it's just not possible!  When you're 16, you can feel like you know yourself, but it's not possible, to be honest.  You have your whole life ahead of you.  Of course, you can pinpoint certain things about yourself that you feel you are.  Finding them is mainly just encountering a new experience, and reflecting upon it.  After quite a few experiences, only then can you start to evaluate them all and make a final decision.

That's just my two cents, at least.