Wisdom is gained by experience, not from books or teachers. Those can only provide guide posts pointing the way. It is up to the individual to learn from their mistakes and to move forward, because to avoid the lessons that life has to offer is to stagnate, to be condemned to repeat the same circumstance over and over until the lesson is learned. Wisdom or folly is a judgment based on what? Something some one told you or something you read? I don't think life works like that.