For many years I over shot. As fatique begins to set in, you begin to fight the Bow.-- You wrestle w/ it-- Trying to MAKE it happen, as opposed to LETTING it happen. Your mind becomes active and and questioning-- What am I doing wrong? Focus on the target suffers, but most importantly, FLUIDITY goes out of your shooting. It is time to put the Bow up. This loss of Effortless, smooth fluidity is a clear, certain message from "inner space" telling you to STOP.
AS far as probs. w/ 3D - They are the same as experienced by all beginners, they will diminish over time. Right now, when you get on the 3D course, you are not fatiqued-- but the first thing you start doing is trying to MAKE it happen-you start pressing mentally and physically, you tense up, and the fluidity is not going to be there. The fluidity is there when you stump shoot, isn't? That's because you are relaxed and having fun, not trying to score some points, or avoid embrassing yourself by wiffing. Approach, 3D in the manner you do stump shooting, and things are going to go alot better.- Afterall, they are just stump shoots with super nice, interesting targets. AS Shivers Irons(Golf in the Kingdom) would say--"Let the nothingness in to your shots". This book is an excellent read for instinctive archers, though written for golfers and fans of the "metaphysical.