As I drift through middle age, the meaning of “sustainability” takes on a very personal connotation. Middle age is that stage in life when you keep telling yourself, “you look pretty good,” while others are thinking, “man, he is showing his age.” It is when your son wants to teach you to kite surf on vacation and you are totally content just watching him from the beach.

Personal sustainability, like every other form of sustainability, is all about that rather maligned word “prudence.” It simply means to make decisions in the present based on what the reasonable outcomes of those decisions will be in the future. When I was 19, jumping off a 50-foot cliff into the sea or surfing in pre-hurricane conditions did not require the kind of prudent consideration it does for me today; though at every age, wisdom and prudence are keys to long-term health and prosperity.

Unfortunately, without prudence, sustainability slips away from us, and we can forge individual and collective prisons of our own making.

In Thomas Costain’s history, The Three Edwards, the author describes this principle graphically. During the 14th century, Raynald III was a duke in what is now Belgium. As the result of a violent quarrel, Raynald’s younger brother Edward mounted a successful coup d’etat against him. When Edward captured Raynald, he built a room around him featuring windows and a door in Nieuwkerk castle. Edward promised him that the day he left the room his title and property would be returned to him.

The problem with this arrangement was that Raynald had what we could describe as an eating disorder. His nickname was “Crassus,” which is Latin for obese, and he could not fit through the openings in the room. Raynald simply needed to lose weight to leave. Edward however, knowing his older brother’s weakness, laid out a sumptuous buffet for him every day. As you may imagine, Raynald’s weight went up, not down.

Anytime someone accused Edward of ill treatment of his brother he said, “My brother is not a prisoner. He may leave when he so wills.”

Raynald stayed in that room for 10 years and only gained his release after Edward was killed in battle. Regrettably by then his health was so deteriorated he died within a year.

Sustaining our personal wellness, our interpersonal relationships and this shared environment we enjoy in such a way that it is better than how we found it is a sacred trust. That trust is only realized when we prudently look at how our actions in the present will impact ourselves and others in the future. ◆

Without prudence, sustainability slips away from us, and we can forge individual and collective prisons of our own making.