Culture: the way we do things here. Is enthusiasm a priority of your team culture? If so, you might add forgiveness as another priority. Without it, enthusiasm flies out the window as soon as things go south.

Forgiving people are happy people.

Athletes perform better when they are having fun.

Forgiveness does not require reconciliation or excusing what happened. Forgiveness is something you do by yourself and for yourself. It provides freedom from distress and the potential to focus completely on something else, such as W.I.N. (What's Important Now). 

Douglas Adams would say:

Don't sweat the small stuff.

It's all small stuff.

Why is forgiveness more common and appreciated in other settings than in sports? I believe it is the intolerance of mediocrity that is so common among great athletes and coaches. Forgiveness does risk acceptance of mediocrity, but that risk is simple enough to avoid by following the advice of Coach John Wooden: "Strive for perfection, but never expect it."