We've all been there: we're on our last set of squats, or slowly trudging through our last mile, when we hit the wall. That's where the wise words of ballerina and Under Armour spokesperson Misty Copeland come in. Like any elite athlete, Misty …

We've all been there: we're on our last set of squats, or slowly trudging through our last mile, when we hit the wall. That's where the wise words of ballerina and Under Armour spokesperson Misty Copeland come in. Like any …