Barry,
This is something I puzzle over constantly.
I'm leaning more these past year to believe confidence for the moment of truth is more about experience... when I was actually hunting where I saw deer and had shot opportunities, I took shots and made good kills. That created confidence and I did better in subsequent years.
Success bred confidence. Hard work and regular practice kept that recent success burned into my sub-conscious.
Due to economic factors, I ended up having to hunt less reliable places, saw few deer, had almost no shot opportunities and now, I again find in the cluth, I question my ability unless it's a slam dunk close shot.
That and the latest place I hunted with good opportunities, is small and bordered by a property where we couldn't retrieve shot deer...and that played badly in the back of my mind, causing me to hesitate...but it was good seeing deer again!
I would think all the pre-visualization stuff like the sports guys do has to help...but from where I am personally, I'm also thinking there has to be "successes" that are fresh in one's mind to help conjur up those images in a believable way.
I only got to one 3D camp out and shoot this year and that really hurt too...making all those shots under tough conditions at shoots, with guys bantering and pestering, always helped build confidence for the real thing.
Experience: That seems to be my confidence builder for the moment of truth.