It's so much easier to learn something the easy way, i.e., by precept, than to have to learn it by cruel experience, not knowing any better in the beginning and having to backtrack to get things to work the way they should have from the start.
It seems to be common to the human experience, this having to pay the price in terms of time, frustration, and, at times, additional resources, to learn something the hard way, taking a turn down some road that looks inviting only to meet a brick wall that we didn't expect, then realizing that we have to go back and do it over again.
Human beings seem to be wired to sometimes have to learn the right path to results by first getting off on the wrong foot ... by wasting some of their effort.
It's all part of the learning process, just like learning how to play chess.
Simply understanding all the rules of chess and how the chess pieces move on the board doesn't win us a game; it seems like we have to lose our first ten games to an opponent before we learn enough to win our first one.
Even young J.S. Bach, in his day, without the benefit of electronic technology and instant learning, no doubt went through some of the same thing.
As he began composing around the age of 15 to be a creator and not just a consumer of music he undoubtedly encountered a blind alley or two, at first, with his own writing ... things that started out good enough, then came to a dead end (photo) ... things that just led nowhere ... wasted paper and ink that demanded backing up and trying again to get where he wanted to go ... all because he didn't know, at the time, how to best work his way around a certain problem.
All of these nearly wasted first attempts have an up side too.
At least, it did for him.
It's one of the things that made him a great teacher.
When you're teaching instrumental music, you're involving yourself with two things: firstly, identifying what the problems are, if any, with what your student's doing, and then, secondly, trying to figure out what in the blue blazes you're going to do about it.
Someone who's encountered a dead end or two in their own experience is in a unique position to teach someone else about what leads to results, what repays the time spent, and what does not.