As a second-grader, my youngest step-daughter was the Energizer Bunny. To help her let off steam, I took her to the local high school tennis courts, where we'd hit the ball back and forth over the net -- sometimes 100 times without missing. I got most of the exercise, since she still held her tennis racquet with two hands and could only swing forehand. No matter where her returns landed on my court, I had to retrieve them and return them with one gentle bounce to her forehand. Even after an hour, she always asked to play longer, and we often did.
As she grew older, I showed her how to hold her racquet with one hand, and how to swing backhand and how to launch an overhead serve. She was a quick study, and by middle school she didn't need me anymore. She was manager of the school tennis team. In high school she played varsity tennis -- a girl to be reckoned with. Recently I learned she's teaching her second-grade son how to play tennis, and like her, he's a quick study.
The happiness I felt when I learned this gave me an clue how our heavenly Father must feel when we do the things He's taught us, like love our neighbor as ourself; love our enemies; care for widows and orphans, and live in the light of His truth. I bet He forgets all the messes of the past, and tells anyone who will listen, "That's MY child!"