In sustained and repetitious physical work, one objective is to get the task done quickly. But to do something right quickly, one needs to start slow so as to first get good technique. Otherwise one plateaus. If one achieves good technique early, one can get faster without hitting any blockages.
Here criticism from someone further advanced is a great gift: a potential blockage is opened up before one reaches it and plateaus, at which point one may no longer be able to detect the blockage. Here one would only experience frustration and confusion, at least until the mistake is discovered and one can continue getting better skilled again.
