McKayla Mulrooney shocked fans and critics alike when she briefly scowled on the awards podium at the 2012 London Olympics after having received a Silver medal for the vault competition. Some saw her as an ungrateful brat, while worse yet, some saw her as a shining example of the youth of the United States, complete with sense of entitlement.  What I saw was a flash of disappointment on the face of a 15 year old girl who had worked so hard and was upset with herself. Years of coaching my three children in football, basketball, and volleyball have taught me a lot about hard work, what winning feels like, and what can be learned from not quite achieving our goals. Last month we received…