I don't think we should beat ourselves up over it- that is, if we place our arrow where we are aiming, (are aiming in the right spot) and still lose the deer.
I don't think we should beat ourselves either but I think a lot of times we are too proud to simply admit that we didn't do it right and we make excuses. I hear it alot and I'm frankly growing a little tired of it. To me, if the animal doesn't die right away, at least to some degree we screwed up. I don't buy the attitude that "I did everything right, got a perfect hit but..."