Sometimes my wife and I finish each other’s sentences. In over thirty years of marriage we’ve become increasingly familiar with the way the other thinks and speaks. We may not even have to finish a sentence at all; just a word or a glance is enough to express a thought.

There’s comfort in that—like an old pair of shoes you continue to wear because they fit so well. Sometimes we even refer to each other affectionately as “my old shoe”—a compliment that might be difficult to understand if you didn’t know us well! Through the years our relationship has developed…