There’s a world of difference between the words “should” and “must.” When my wife tells me I should exercise more, I know she’s right. It’s good advice. But there’s still a sense that I have a choice. On the other hand, after I experienced an atrial fibrillation episode while preaching recently—something dehydration may have contributed to—my doctor told me I must drink more water. That wasn’t a suggestion. It was a necessity.