I have always found it interesting that the images that I have either sold or are the most liked by others are images that I just happened to catch out of the corner of my eye or maybe saw on my way back home from shooting the "important stuff" with one last film holder left in the bag. Or I have a few frames left on another camera and see something sort of interesting and after getting home it is the best image on the roll.
for example, I can head out early with a couple of scouted subjects in mind. The light is right, I have the right film, lens etc. Another day I can be just traveling in the car with my gear and see something on a road I had traveled 100 times and something in the distance or just the curiosity of a gravel turn off interests me and then I find something that produces a great image. the latter images always seem the better.
I know that chance favors the prepared mind, so maybe I just try to hard for some images. I am curious as to how others find their best work, planning ahead or finding things by chance?