One day the father of one of our kindergartners joined me in watching his son wrestle for fun with another 6 year old outside on the grass. It was fun to watch because they were having a good time wrestling as friends, much like dogs having fun play-fighting.
After a few minutes, the boy's father watched him accidentally twist his ankle, resulting in the little guy crying in pain. His father and I went over and made sure he was okay as the other boy was clearly sorry by apologizing to him over and over. He was okay, but still obviously in pain.
I mentioned to the father, who was comforting his son by rubbing his back, "Well, maybe no wrestling next time."
He reassured me, "No, it's fine." After a brief pause, he added, "We've got to nurture them, not neuter them. Right?"
"Very true," I smiled.