laughter plus compatability.

"One of the keys to compatibility is laughter. Laughter tells you how much you will enjoy each other’s company over the long term. If your laughter together is good and healthy, and not at the expense of others, then you have a healthy relationship to the world. Laughter is the child of surprise. If you can make each other laugh, you can always surprise each other. And if you can always surprise each other, you can always keep the world around you new." -Kent Nerburn