-experience of over coming setbacks and obstacles -is included to suggest that occasional, real experiences of solving a problem, re-making something that was not successful the first time, and other experiences of overcoming difficulties can strengthen a child's confidence and become a lifelong disposition.
I see a lot on the internet about how we need to teach children "real skills" and I think this could be one of the best to teach. Rejection and failure are a natural part of life, our job is not to maneuver children away from problem, but to guide them through conflict towards peace and understands.