Brad Stolbach, a trauma psychologist at the University of Chicago, said this kind of trauma often takes on a life of its own.

“That experience, in a lot of ways, it lives by itself,” he told me last year while I was working on a story on the impact of trauma in young people in gun-weary Chicago. “It doesn’t get integrated with the rest of your memory, the rest of your brain, the rest of yourself. Then we go to great lengths to keep it out of awareness.” If we don’t find ways to integrate a near-death experience, it can change the way we live. “We function as if we are in there, in that moment, under constant threat, as if it’s still happening to us, or we function as if it never happened,” Dr. Stolbach said.

I was reminded of Ahriel Fuller, a young woman I met a few years ago in Chicago. She had survived being shot when she was 6 years old. She told me that even more than a dozen years later, it was as if that bullet was still screaming toward her.

She sat among a group of nearly 20 other young people who all recounted stories of witnessing shootings and beatings or being victims of them. A group of young people in folding chairs, with earbuds dangling from their necks, who could talk matter-of-factly about what it felt like when the bullet pierced their stomach or they saw people they loved being gunned down. These kinds of memories, they said, clung regardless of how hard they tried to shake them.

“It never leaves you,” Ms. Fuller said. The challenge is not to become numb.

A blood clot and a bullet are very different things. But both have the ability to take or shred a life. The physical and emotional toll that both can leave on their victims and those who witness them can be lasting. Both take a physical toll — that is obvious — and an emotional toll, which is sometimes less evident. And both require attention.

Fortunately, I’d suffered only minimal heart damage, but enough to leave me exhausted most days. After months of cardiac rehab, running on the treadmill, lifting weights and tugging at the rowing machine, I slowly began to repair the physical damage that was done. But the emotional rehab continues.

About seven months ago, exhausted and stressed out, I stood up too quickly and suffered syncope, medical jargon for passing out. When I came to I was lying in my hallway in a pool of sweat. My wife was clutching my face, again, wide-eyed and terrified. I thought I was dying. I called my daughter close and told her that I loved her. I said what I’d said dozens of times before at her bedside: “You’re going to do something special one day.” She nodded a yes. “Do you believe it?” I asked.