I showed it to a friend not too long ago and their response--"Wow, you haven't changed much."
So, the point is, throughout our lives I believe our inner nature stays the same. Maturity plays a huge role in how we act in certain situations (because if I were in a wedding today, I'm pretty sure I wouldn't throw a tantrum) but there's this part of yourself you will never lose touch with. You can say you've changed on certain levels, maybe you have a new set of opinions on a matter or made some drastic lifestyle changes, but ultimately the qualities of your mind will remain the same.
Tim O'Brien uses eyes as evidence of this-"I know my own eyes"(236). I think most people could look at a photo of themselves at an earlier point in their life and automatically recognize the fact that they still have the same gaze. Describing the essence of oneself can get to be a kind of strange concept, but seeing how ones eyes are unchanging from birth to death makes it more concrete.