Imagine the dark arriving at the edges first. A faint narrowing at the corners of everything you see, so slight you tell yourself you imagined it. Then it is not slight. It creeps inward, month by month, month after month, the periphery folding toward the center, until the last bright circle in the middle closes like an aperture and does not open again. You spent thirty years watching the world. Now you will spend the rest of it in the dark.

This happened to one of my dad’s best friends. A lawyer, a mentally and physically healthy man. There was no warning, or anything he did anything to deserve it. An incurable disease simply took his sight in his thirties. You know the version of this story you expect. Bitterness. The “why me?” The slow souring of a man robbed of something he had every right to keep.

But he is the opposite of bitter. He is in his sixties now, blind longer than he was sighted, and he is one of the most alive people I have ever been near. He still runs his own law firm. He kayaks and rides a tandem bike every week, and he even signs up for the hardest, most brutal bike races in northern Mexico. He greets me the way a sighted man would, warm and quick, "you've gotten so tall," and he tells my wife she's beautiful and says he loves the sunset, and he means all of it. He talks like a man who still sees, because in every way that matters, he does.

He had every reason to go dark on the inside too. And he refused.

That refusal is the most powerful thing a human being can do, and it decides more about a life than circumstance ever will. Swami Vivekananda, the Hindu monk who carried yoga to the West, made the same demand of anyone serious about the inner life, and he had no patience for the long face some people mistake for depth. "It is the cheerful mind that is persevering. It is the strong mind that hews its way through a thousand difficulties," he wrote.

My uncle never read that line, and yet, he embodies it. The one thing no disease and no accident and no loss can reach is the attitude you decide to meet it with. Everything else can be taken. That cannot be taken. It can only be surrendered, and he never surrendered it.

Sight is a precious gift. But the way you choose to see has nothing to do with the eyes.