Although I do not shoot 1 arrow per group, I do analyze every shot. I have been shooting for long enough that I can usually "call my shot". What I mean is as the arrow leaves the bow I can generally tell whether it is going to be on, right, left, whatever. This is why I like practicing 90% of the time at 50 and 60 yards. It is truly amazing how much different it is shooting at 50 compared to 40 and 60 compared to 50. The difficulty, and resulting group sizes, are not linearly related. It is definitely an exponential curve.

I can say that 99% of my errant shots are due to a bad release or dropping my bow arm at release. The first is the one where I am cussing before the arrow gets to the target