The ceramics teacher announced on opening day that he was dividing the class into two groups. All those on the left side of the studio, he said, would be graded solely on the quantity of work they produced, all those on the right solely on its quality. His procedure was simple: on the final day of class he would bring in his bathroom scales and weigh the work of the "quantity" group: fifty pound of pots rated an "A", forty pounds a "B", and so on. Those being graded on "quality", however, needed to produce only one pot - albeit a perfect one - to get an "A".
Well, came grading time and a curious fact emerged: the works of highest quality were all produced by the group being graded for quantity. It seems that while the "quantity" group was busily churning out piles of work - and learning from their mistakes - the "quality" group had sat theorizing about perfection, and in the end had little more to show for their efforts than grandiose theories and a pile of dead clay.
From Art and Fear, David Bayless and Ted Orland ht LW.The obvious caveat that the cost of practise cannot be too high. You probably don't want to try the throw it against the wall and see what sticks methodology with skydiving. When you have practise with a potential for severe negatives (football, skydiving, live-round combat) there is likely to be a point of diminishing returns on the more costly forms of practise. Thus football teams don't practise full contact every day.
Back when I was in Junior High, I did play for a football team where the coach decided to toughen us up by full contact practise all week. Some of our already mediocre talent was hurt and we still were not very good: but it was fun.