Edward Weston once said something about how, when he started to think, he stopped photographing. Writers know the problem Donald is addressing - it's referred to as The Editor or The Critic. You're writing along in a groove and The Editor suddenly stops you with "That's no good." Or "So-and-so wouldn't write it that way."
We have the same thing with photography - as Donald said, the mind fills in and stops the seeing. How to move beyond this? I don't know yet.