Deep Question.

On the issue of really knowing yourself:

Most people are lucky enough to not know themselves, or at least not know their limits. If you get really introspective, there is the part of yourself that is familliar and makes you feel good, then there is the part that is hidden in the dark. By the time you are 17 you should have a pretty good handle on the "good" part. It is the part in the dark that you just can't see. I'm not saying go out and do things you know are bad to get to know yourself, because that will just reinforce what you already know. The times your really learn about yourself are when you do bad things that seen perfectly acceptable in the moment, then regret them later. I guess you could say regret is the only teacher. You may think you have regrets now, but (I'm guessing here, I don't know you) I don't think you have ever really had to "push the envelope". Think of Nazi soldiers who stuffed Jews into the gas chambers - knowing it was wrong, but discovering that they were not strong enough to face death themselves by disobeying. Consider the crack addict who blew some stranger in an alley to pay for his next rock. Consider the alcoholic who got drunk while his wife packed-up his starving kids and left him to go live in a shelter. These are all people who know their limits because they have been pushed past them (or right up to them).
I think Dan hit it pretty square when he spoke of the critical mass of life experiences. 30 is a milestone, but it is milage rather than years that makes someone who they are.
When I was younger, I read a lot, still do, when I can find the time. A couple of books that may help are The Stranger, Camus; and Crime and Punishment, Doystievsky(?). Neither will give you any insight into yourself, but show you the road to self-discovery. Both are about self-centered people, who do something they know is wrong, but decide they can handle it anyway, and the consequences and remorse that illuminates a part of them better left in the dark.
99% of the time an epiphone of the self is not a pleasant discovery, and not something that can be captured. It will come to you, when you least expect it.