Garry Winogrand said something I can definitely relate to in my attempts at learning to photograph.  

He said, "Photographers mistake the emotion they feel while taking the picture as judgment that the photograph is good."  

So many times I've felt something was beautiful, the light was perfect, and so on, only to find the resulting shot fell far short of what I thought I'd seen.  I've always felt this gap was a measure of my shortcomings as a photographer, and closing it would mean getting the actual photograph closer to how I imagined it should look when I took it.  So it's a bit heartening to find that someone as accomplished as Winogrand was at least aware of this tendency.

By the way, Winogrand also famously said he photographs to see what a thing looks like photographed.  This underscores how the photograph is something distinct from its subject.  I've found it can be good to just photograph things I feel like shooting in the moment, even when I don't know why.  Just do it without thinking too much.  I can go back to those photos later and look for patterns, perhaps finding out what it was that interested me even if I didn't realize it at the time of shooting.  And maybe even go back to that same place or thing later.  There is no need to think too much.  In fact, thoughts can become impediments in the moment.