I never agonize over perfection while taking a shot. I stay in the moment, keep moving and looking and experimenting . I do find that sometimes when reviewing shots later I have a lot of "if I had just" revelations. If I had just squatted down and shot up. If I had just composed the shot like so. If I had just used a different f stop. If I had just had the camera set properly beforehand. If I had just.... But in between all of those "if I had justs" are a few shots that make it all worth it.