I was 28, a professional living in Palo Alto, six months into my marriage, when I suffered a stroke in my sleep.

It was a surprise. I’d been a college athlete and marathoner.

The diagnosis was idiopathic dilated cardiomyopathy. To translate to English: heart failure. The doctors didn’t know why, but my heart’s ability to pump blood was so diminished that I needed a new heart. The doctors weren’t sure when I would need the transplant; it could be eight years or eight months.

I was admitted to Stanford University Medical Center, and my condition continued a rapid decline. In a matter of weeks, I lost nearly half my body weight, my lips turned blue, and my skin took on a yellowish hue. I was dying.

The doctors listed me for a transplant, and the wait began. Would I get a heart in time? As I passed in and out of consciousness, I heard stories about people on my floor who were also waiting for hearts. Several died. I prayed for a new heart. I envisioned running another marathon. I pictured camping with my wife, Kendall, in the Sierras. I even prayed for rainy nights, which would increase the possibility of accidents and donors.

Shortly after 1 a.m. on May 2, 2001—eight weeks after my diagnosis—a doctor opened the door of my hospital room. He was short and wore a surgical cap.

“We have a heart for you; do you want it?”

I asked if my friend, Dr. Marc Pelletier, would perform the surgery. The doctor, standing in my doorway, raised his eyebrows, glanced at the many beeping machines keeping me alive, and smiled. He nodded yes.

In the course of our brief exchange, it hit me. I was getting the gift of a lifetime. With tears in my eyes, I said I wanted the heart.

I punched the numbers on the phone next to my bed. My voiced cracked as I told my wife they had found a heart for me. In minutes, she was sitting next to my bed.

I had to wait until morning for the surgery. During those seven hours, I was at once terrified that I might not survive the surgery, hopeful that I might regain my life, and grateful that I was being given this incredible gift.

And sad, deeply so, because I knew my chance at life meant that someone had died.

Across the Bay, two parents were having a very different night. Their eldest son, Tommy, had been killed in a car accident. I later learned that he was a much-loved 19-year-old youth minister. His first priority was helping others, yet God had chosen to cut his life dramatically short.

On the worst night of their lives, Tommy’s parents thought of people in need, people they had never met, people who desperately needed Tommy’s organs. On May 2, Tommy saved six lives, including mine.

I awoke from the transplant with an overwhelming, almost crushing sense of guilt. My prayers for a “rainy night” had gone answered. I spent entire days in tears. I met with psychiatrists and priests, but nothing assuaged my overwhelming survivor’s guilt. At the very least, I wanted desperately to thank the family that had saved my life.

To prevent additional emotional anguish, Stanford closely monitors communication between recipients and donor families. When I wrote a letter of thanks, I gave it to an intermediary, a social worker, who in turn passed it on to the donor family. For the next nine years, I sent them a letter of thanks every May 2. I realized that the family might not want to hear from me, but writing the letters brought me some small solace.

Nearly 10 years after the transplant, I received an unexpected letter from my donor’s father. We corresponded with some regularity over the next few months, and, in mid-May 2011, I met Tommy’s dad in a pizzeria. Tom Sr. was a tall, muscular man. His eyes welled up when I walked in holding my 2-year-old son, Lane. My wife held our 6-year-old daughter, Carlie, by the hand. I put Lane down and gave Tom an awkward hug. It wasn’t long before Lane was sitting on his lap.

That day, I was able to say thank you in person. I told Tom Sr. I’d been practicing for this moment for the past 10 years.

A year later, I met Tommy’s mother. I hugged her for nearly 10 seconds. When she talked about her son, she smiled and wiped her eyes.

You know that feeling you get when you see someone in a military uniform and you have an overwhelming desire to say thank you? But you know that saying those two measly words isn’t nearly enough? That’s what saying thank you to Tommy’s parents was like.

I could never tell them how much their selfless act has meant to me. But it was a start.