When you run into someone who is disagreeable to others, you may be sure he is uncomfortable with himself; the amount of pain we inflict upon others is directly proportional to the amount we feel within us.
A famously wise old man in a village was once asked how he came by his wisdom. "I got it from my good judgment," he answered. And where did his good judgment come from? "I got it from my bad judgment."
Parents - and teachers too - are woefully short-sighted when they try to protect the child from his mistakes, when they make the "right answer" more important than the quest for knowledge and good judgment. For what is not learned within one's self cannot be learned from another.