You have started a great thread and some of the folks have suggested some excellent ideas. Mike has really hit the nail on the head with the question of "What do you want?"
The statement of documentation, suggestion of a way of life, a reminder of what the world is about, maybe a path to follow; all may be motivating factors. I shoot a lot of photos with the idea of documenting a moment in time. Then as I view what I have, I pursue a more specific meaning. Sometimes, my best ideas fall under the "delete" key. But, as Mike has suggested, what story do you want the photo to tell?
Having said all this.... a lot of the time I do not have an answer to this question until late in the photo's development. Probably would fail Mike's class.... But, we all keep trying, looking, thinking about what we are about, what we want to say. And that is where the fun is!