This is a huge subject, what costs us all targets is part psychological part mechanical, almost everything that blights and ruins a given persons scores will also cost others
enough dropped targets to put them out of placings.
Flinch, too relaxed, not enough alertness, too much thinking, under-thinking, over leading, poor address, poor pick up, hesitation, shooting too quickly (through fear of not knowing what else to do), lack of follow through (not finishing the shot) will cost you when you eventually mistime your dismount by lifting and abandoning the process too early, forgetting last weeks lessons/errors, not having the ability/experience to make micro corrections during even successful shots, poor transition, poor selection of first bird of a simmo, lack of
confidence will also cost you birds that you can actually hit all day
etc, etc,.
FWIW if I had to pick a couple of things that seem to affect more or less everyone, it is the inability to detect and compensate for quartering targets and treating them as crossers, plus putting more emphasis on
lead than they do on
line.
Poor lead will often still break one or even two, poor line will miss them all.
If I had to cut to the chase and tell the truth without fear of hurting feelings, it is that we miss through basic lack of shooting skill, yes I have stolen that from George Digweed but only because I agree with it.
ps. must qualify everything and also state that we all have a certain ability level beyond which we seem incapable of meaningful improvement, that plateau is damn hard to break out of without zillions of practice hours.