A concept most clearly articulated by the best Scout leader I ever had:
"Never stand in the way of a learning experience."
Counterpoint: as my creative management tutor said it:
"When you drop a concrete block on your foot, it's difficult to think of it as a learning experience."
Experience is a dear master, but fools will learn at no other. --BenjaminFranklin
The key to training in this way is to set things up so that the experience is painful enough that the recipient learns the lesson, but not so painful as to be damaging in more than a minor way. If you see someone about to drop a concrete block on his foot, don't stop him, but see if you can't manipulate the situation so that he ends up dropping a rather smaller rock on his foot. --CurtSampson