Children in their natural state are totally focused on pleasure. They aim to maximize the FUN in every moment. We can learn a lot about practical happiness by observing them.
For example, when kids are playing a ball game, and the ball lands too close to the line to tell if it's "in" or "out," they don't waste their time and energy arguing about it. There's no fun in that!
Instead, someone calls out, "Do-over!" and they all return to the beginning of the last play to have another go at it.
The do-over is a great tool for parents, too. When an interaction between you and your child turns sour, just stop, remember that you'd rather feel good than be 'right,' and say, "Let's have a do-over!"
Then you can redo the interaction with a clear intention to enjoy it.
My wife and I use do-overs with each other, too. It's way more fun than fighting!