I feel a sudden clear focus and perspective. There is no time for anything inessential. I must focus on myself, my work and my friends. I shall no longer look at “NewsHour” every night. I shall no longer pay any attention to politics or arguments about global warming. This is not indifference but detachment — I still care deeply about the Middle East, about global warming, about growing inequality, but these are no longer my business; they belong to the future. I rejoice when I meet gifted young people — even the one who biopsied and diagnosed my metastases. I feel the future is in good hands.

But in the weeks after I learned that the breast cancer I have been in treatment for over the past year had spread to my bones — breaking my spine and becoming incurable and most likely fatal — finding the perfect living-room couch has begun to feel like the most important thing I’ve ever done.

Let us consider me as a test case. As I have said, I would like to die peacefully with Thomas Tallis on my iPod before the disease takes me over and I hope that will not be for quite some time to come, because if I knew that I could die at any time I wanted, then suddenly every day would be as precious as a million pounds. If I knew that I could die, I would live. My life, my death, my choice.

what’s the difference? If I die in two years’ time, what will I do between now and then which I don’t want to do now? The main reason for living longer now is for the sake of my family and my wife. And this is not rationalist bravado entirely. I’ve had a wonderful life. Yes, I’ve done a lot of things I shouldn’t have done. But you know, I’ve had a full, complete life, and there’s nothing more I can do to complete it. Dying when you’re younger is obviously a totally different situation. Or losing a child. I mean, that’s beyond words.

I did the things you might expect of someone whose world has suddenly become very small. I sank to my knees and cried. I called my husband at our home nearby. I waited until he arrived so we could wrap our arms around each other and say the things that must be said. I have loved you forever. I am so grateful for our life together. Please take care of our son.

The movement has perfected a rarefied form of America’s addiction to self-rule, which denies much of our humanity: our fragile bodies, our finitude, our need to stare down our deaths (at least once in a while) and be filled with dread and wonder. At some point, we must say to ourselves, I’m going to need to let go.

But cancer has also ushered in new ways of being alive. Even when I am this distant from Canadian family and friends, everything feels as if it is painted in bright colors. In my vulnerability, I am seeing my world without the Instagrammed filter of breezy certainties and perfectible moments. I can’t help noticing the brittleness of the walls that keep most people fed, sheltered and whole. I find myself returning to the same thoughts again and again: Life is so beautiful. Life is so hard.

To so many people, I am no longer just myself. I am a reminder of a thought that is difficult for the rational brain to accept: that the elements that constitute our bodies might fail at any moment. When I originally got my diagnosis at age 35, all I could think to say was, “But I have a son.” It was the best argument I had. I can’t end. This world can’t end. It had just begun. A tragedy is like a fault line. A life is split into a before and an after, and most of the time, the before was better.