There is an ideal state between tension and relaxation that makes it possible to play the piano well. The shoulder, arm and hand must be relaxed but not limp to play smoothly and evenly without fatigue or injury. The same is true for singing. The throat must be open, but the diaphragm must be engaged and toned. Music itself is full of the balance between tension and release. As a piece progresses the listener searches for the familiar--the return of a melody or rhythm or harmony--and longs for something new. Skillful composers manipulate that need for unity and contrast so that just when you think the melody or rhythm will go one way it goes another. They introduce the element of happy surprise! Writers do the same thing as they strive to create a story that is logical and plausible but not predictable. They know readers love a cliff hanger or plot twist and they work hard to include them whenever they can.
So much of life is like that too. We need a little bit of stress, what people sometimes call "good stress", so that life is exciting and challenging and we have a reason to get up in the morning. But too much and we shut down. We get exhausted and cranky. As I go about my day I often think of this strange balancing act, the need to keep myself busy enough without overdoing it. Sometimes it seems nearly impossible. But I know that life is an art. I keep trying to add a cliffhanger or two to keep it interesting, but I'm always oh-so-glad when I arrive safely and metaphorically home.