To me, this basically sounds like the "nature versus nurture" debate all neatly dressed up (that is not meant to sound condescending and if I could figure out how to reword that I would, sorry). Though for me, it's never been a debate. We are the product of genetics or an essential core while also being a product of the things we have experienced.
Look at it this way. You may have been born with a shy personality or lanky limbs. Those two traits with definitely effect your war in particular no matter what happens. In this sense, you are not shaped by your experiences by rather your experiences are shaped by who you are.
However, maybe you were born in an African country. Think about that for a second since I am pretty sure that is not where you hail from. (I have no clue where you are from, but based upon what little I know of you this is my conclusion.) Now in certain African cultures, shyness is not seen as a sign of insecurity and weakness as it is in America. It is seen more as a dignified trait almost like being stoic in America, but it's not quite the same. So while you may be a shy person through and through, the opinion you may have of your shyness may be greatly different. The end result of this may be you have more confidence and comfortableness in your own skin if your were born in Africa rather than America. You may end up seeking more autonomy as a African rather a American. I think it can be agreed upon that you were be a different person due to what you have experienced.
I do agree that there is an essential core to everyone that defines them as a particular person, but that core can extend out in all different kinds of directions based upon the experiences we run into.
Now, that is basically my opinion of the lives we lead and our identities. I have another opinion on how you don't seem to place significance on past events.
When I first read your words, I was thinking, "Duh, our experiences affect us." But as your words started to roll through my brain, I realized I have felt the same way at times. There are clear, definite moments in my life when an event, etc has shaped my identity and essence, but there are many other moments when things glaze over me. For example when my grandfather died, I never really felt the weight of his death. I never knew him too well, but he was definitely a presence in my life. Of course, it might be more interesting as to my lack of grief when he died but I think that connects back to significance. I only fretted over how everyone else seemed to be sad around me. If it weren't for their frowns, I would have smiled freely. The event simply didn't affect me. When I entered into college, I didn't feel myself affected by that either. I admit to learning a lot about life sine then, but I have always shrugged college as just another plain and boring event. Though maybe, college has made me more cynical? It has affected my personality in that regard. As for something more mundane, rock concerts seem to be a mere blip in my memory. This is odd because I am rock'n'roll addict, lover, obsessor, and I attend concerts frequently. Though after all is done in said, I can barely remember the nights that are suppose to me cathartic. I am still the same person the next morning when I wake up.
There is one experience, however, that I know has greatly affected me. Maybe it simply uncovered a part of me that has always been there, but I disagree. Recently, I ran into a man that somehow managed to pose a religious question to me in a manner that came off as unique. It really wasn't a unique question, but it got me thinking about the nature of religion in way this philosophy-junkei has never thought about it before. I am not more religious, spiritual, or any or those sort of things because of the man. I am simply more tolerant. This is not to say I have never been a tolerant person, but I have grown to look distastefully upon all religion in recent years. That negative perspective is basically nulled out now. Religion is not something distasteful in my eyes, but rather it is simply another aspect of life and is acceptable as the way I choose to live my life (given of course non-malicious religion is being practiced).
EDIT: After skimming back over the previous posts, I feel like there is something here I am missing. Eh, I was suppose to go to bed two hours ago. Maybe I should do that.... Well, these are my words until the morning since I will of course visit this thread again tomorrow.