It's good to go to a shoot with an idea of what you want to achieve. Pre-visualising a shot is a valuable skill and can lead to some amazing work, especially for a technically skilled photographer. But it can also be a straight jacket. You leave the shoot with pictures that you hope will give you the raw (pun intended) materials to make the pictures you pre-visualised. So when you click through those pictures you're looking for signs that they've got the characteristics you wanted. You reject shots that don't support the idea in your head. If you're very diligent you'll process the winners at this point, publish them and archive away the shoot.
But sometimes, if you can make the time to go back to those pictures 1 month, maybe 2 months later you'll find gems in there that you didn't see before. You'll look at the pictures with different eyes. You won't have that pre-vis straightjacket on any more and hopefully you'll be able to look at the pictures with a clear head - seeing what's good and bad in each on its own merits. Once you can do that you're free to take those RAWs in directions you didn't intend and a whole new kind of art can appear. Some art is made, some is discovered. Most is a little of each.
Above is an example from my recent work. I've been getting as much practice in as I can with portraiture and studio lighting. I attended (rather than taught - for a change) a lighting academy run by Will Cheung, editor of Advanced Photographer magazine, and run by the company that organises my own workshops, Welshot Imaging. We shot 4 different models during those two days - you can see my "keepers" from this workshop in the Gallery - and this shot above was one where we were set up for a dramatic type of light. On the day I saw it as black and white without realising quite what I had in mind. I processed the images from the workshop during the following week and published all the winners. This shot never made the publishing cut because it just didn't look right and I didn't know why.
I've shot a few more model sessions since then and on a whim I was looking back through previous shoots and suddenly it struck me what was wrong here. This was clearly a film noir shot and I'd missed out some of the glow and lighting emphasis needed to make that work. A little tweak in Nik Color Efex Pro and Lightroom and voila - a shot I couldn't see before is now something I'm pretty proud of.