Five years ago, on the eve of New Year’s Eve, I found it. I was showering—just washing, not checking for anything—and the soap moved over my breast in an odd, rough way, like a car bumping over a big rock in the road. Five years ago today, it was confirmed: invasive ductal carcinoma. Breast cancer. That was the beginning. There were days then that I would have wept in relief if you had told me I would be writing about this little adventure on my 5^th lumpiversary. 18% women with cancer like mine don’t get that chance.

Here, from the perch of five years and two cancers (six surgeries, chemotherapy, radiotherapy and enough daily medicines and supplements to make sure I never forget), there are a few things I’ve learned that are unexpected. Sure, I’ve learned the things one expects to learn—that relationships are the most important thing, that stuff matters hardly at all—but there are some things I learned that surprised me, some that chastened me about myself. In many ways, cancer is the most challenging school I’ve ever been to (and I’ve been to a lot of school!). As a friend told me, “I’d love the lessons, but I really hate the teacher.”

Over the next five days, I’ll post these five lessons. Here’s the first one.

Lesson 1. Life is definitely fatal

With breast cancer and a couple of others (melanoma, for example), there are two startling realizations. The first is that you have cancer and it can kill you. Soon. The second is that you have cancer and it can kill you. At any point in the future. Some cancers are never considered “cured” and the threat of dying from them never ends. This second piece of information was actually more horrific to me than the first. With the first, I was a hero on a quest, with my life at risk during the adventure but then, once the adventure was over, the prizes of the journey would be mine. I remember where I was sitting when I found out that the risk didn’t end; i remember the seismic shift in my body. This was not a hero’s journey. This was the base line of my mortality, and it would play for, well, the rest of my life. I realized there was a way I had considered myself immortal, or perhaps it was that I had never considered my mortality, which amounts to the same thing. I fell into mourning for a thing I had never had, but which, upon losing it, seemed to have ruined my life.

One day I decided to get to the bottom of my grief. I went into my study and began to write on little slips of paper the things I was sad to leave behind when I died. I threw the slips on the floor in a ritual designed to get to the bottom of my fear of death. As the little papers mounted, I found myself spiraling deeper and deeper in to the choking misery of grief. It was bottomless. The losses after we die are endless—that’s what mortality means. We stop and the world goes on. We don’t get to see how any story plays out—not even our own. By the end of the ritual I was on the floor with the little slips of paper, sobbing. I had made it worse.

Of course in some ways this is absurd. We will all die of something. That knowledge is with us every day. We all know that we are short-lived, and that history is long. And yet, I realized on the floor that I hadn’t actually known that fully, hadn’t known it in the sob-until-your-stomach-hurts kind of way. Sure, before I was diagnosed with cancer, the envelope of my life was unknown—it could be big or small. But I paid no real attention to that idea until the doctor told me that the breast cancer could come back at any point. This made every day shadowed by the possibility of death; it made mortality impossible to forget. Now I really know I’m mortal.

And wow is there a gift in that. I didn’t find it that day on the floor, but I have found it most days since. Yes there is a new kind of delight in moments I might have overlooked before—the ease with which my dog curls up on his pillow, the feel of my grown-daughter’s body in a long hug, the perfect symmetry of a tiny purple flower in the grass. What’s more surprising is that there is also freedom in how short and partial my bit is. I feel great liberation in knowing that I don’t have to solve it all, that I can do my part and then exit stage left and the other actors will carry on. The world is long, my part is short. I want to play it with all my heart, and also not take it too seriously. It connects me more fully to the other people on this journey along with me—even those I’ll never meet, the ones who came 100s of years before me or will come hundreds of years after me. We are united by our mortality, each of us a tiny part of the huge story that is humanity. It might be the most fundamentally connecting thing humans have.

Our mortality isn’t a curse, or at least isn’t just a curse. It’s a connecting, liberating gift. I had no idea. The gift of the knowledge of life and death is perhaps the most unexpected and delightful present of cancer.