I love it (and hate it) when I have a picture that I know has potential. I can see it and feel it but nothing I do is right. I move it to a separate folder and just sit on it, sometimes for months.
Then one day I'm messing around with another picture, and it clicks what I need to do with the one I've been waiting on. Those moments invigorate me, because I learned a new process, tweak, edit etc... whatever you want to call it, and I'm finally able to take that picture and show it's story.