You're analyzing why you're either drawn to the image or why the image doesn't have any impact on you.
There is an exciting shift that happens in your head and it's hard to explain. When you really grasp the principles of a successful photo, you start to look at every image critically. I don't mean that you're criticizing the image. You're no longer just seeing a subject and composition in a photo. You're analyzing why you're either drawn to the image or why the image doesn't have any impact on you. You're thinking, "what is it that I like about that image and how can I use it in my own work?"