I think that for many who are serious about photography, you go through stages. Early on is the snapshot, create a memory mentality. Then if one becomes more serious they begin to look closer at the selection of subject matter, compositional style etc. I think I can look back on most of my photographs and wonder, why did I take that? What part of me finds this to be interesting enough to explore with a camera? We create many images that reflect something of our inner selves, yet we don't really understand why or exactly what we are trying to express.
Those that make it to the next stage (Brett and Ed Weston, Strand, Callahan, Evans or Morris to name a few) understand what it is within them that makes them photograph and have learned to use the medium to create a window into how they see the world and the image is their commentary. I think the great ones see something or search out something to photograph that resonates with them, and they know why it does. They know the real work involves taking that subject and creating an image that translates their inner self into something that conveys that message to others.
In the final stage, the photographers best images become the equivalent of another artists poem or short story. Maybe the photo conjurs up cool jazz sounds or African rhythms.
I am like dnmilikan. On that road of self discovery, learing how to use the medium to express a feeling, a point of view, present my ideas on paper, and in the process show a little bit of my past, present and future.