If not for running, I might not be alive today. I mean this quite literally. On more than one occasion, I have successfully escaped from someone who was chasing me on foot with a knife. But running has saved me in a different way, too, giving me the strength I needed to support the person I love through a long ordeal that challenged us both to the point of breaking.

You see, the person who chased me with a knife, more than once, was my wife.

I met Nataki on a blind date at Oakland’s Jack London Square in 1997. I was 26 to her 22—a modest age gap that was, in fact, our greatest demographic commonality. Why our mutual friend should have thought to set up Nataki, a churchgoing African American hairdresser from the inner city, with me, an irreligious white guy from a backwoods New England college town, I will never know. But we hit it off and were soon going steady.

I remember the moment I decided that Nataki was a keeper like it was yesterday. We’d been dating for four months when I took her to my hometown of Madbury, New Hampshire, to celebrate Thanksgiving with my family. Before dinner, Nataki, by her own initiative, fed hors d’oeuvres by hand to my grandmother, who had advanced-stage colon cancer and severe dementia and was unable to feed herself or communicate verbally. It was a beautiful moment, and it made me realize that I would live a richer, more authentic life with Nataki than without her. We may not have been much alike, but I loved her because I wanted to be more like her—fearlessly real.

In those days I wasn’t running, having quit the sport nine years earlier. As an adolescent athlete, I was fainthearted to a degree that spoiled a once promising high school sports career. It wasn’t the pressure to win that I shrank from so much as the lung-scorching pain that’s an inescapable part of getting from start to finish in the shortest time possible. Like an actual, physical heart condition, this faintheartedness worsened by degrees, causing me to regress from leading a state-championship-winning cross-country team as a sophomore to intentionally missing the start of an outdoor track race as a junior to giving up running—forever, I presumed—a few weeks before my graduation in 1989.

You see, the person who chased me with a knife, more than once, was my wife.

But I was eventually drawn back into racing. In 1998, some 15 months into my relationship with Nataki, I did a short triathlon as a lark, during a rum-soaked junket on the Caribbean island of St. Maarten, humiliating myself with an almost last-place finish while my sweetheart looked on. This painful flop reopened hidden wounds incurred in Act One of my life as a long-distance racer and inspired an unexpected second act. Within six months, I had become a full-blown endorphin junkie, logging ever more training miles in pursuit of ever more ambitious goals, determined to become the brave competitor I hadn’t been as a teenager. I qualified for the Boston Marathon, completed a full Ironman, and earned USA Triathlon All-American status by placing in the top 10 percent of my age group nationwide.

Nataki, meanwhile, found a passion of her own in Charismatic Christianity, a form of the religion in which believers have faith that miracles, healing, and direct signs from God are part of everyday life. In the beginning, this new spiritual direction brought her great happiness—a fulfillment that seemed not unlike what I got out of my quest to discover my physical limits.

But then something changed, and Nataki’s spiritual eagerness transformed gradually into a kind of desperation. We’d been married for two years when, on a 2003 trip back east for the holidays, Nataki informed me that she would take her meals apart from my family because they weren’t “saved.” I talked her out of the idea, but I couldn’t help wondering: Was this the same person who had spontaneously fed my dying grandmother six years before?

In a sense, she wasn’t. By the spring of 2004, Nataki’s unraveling reached a crisis state. She became convinced that the apocalyptic rapture that many Christians believe to be foretold in certain scriptures had begun, and that she had been left behind with me and all the other hell-bound heathens. It was clear she needed help—a kind of help I couldn’t offer—and I somehow persuaded her to see a psychiatrist. As luck would have it, though, this happened on the Saturday of a long Memorial Day weekend, and her calls went unanswered.

The next evening, I made turkey burgers for dinner. Nataki took one bite of hers and spat it onto her plate.

“It tastes funny,” she said.

A chill ran through my body. I knew immediately that she believed I’d poisoned her food. I assured Nataki that nobody had tampered with her burger and offered to swap plates. In response, she burst into tears. I watched in horror as Nataki’s bawling morphed into a kind of seizure, her torso convulsing jerkily, her chin jutting forward with each spasm, her lips issuing a mournful vibrating sound.

I moved a comforting hand toward her shoulder, but before it got there she leapt up from her seat, clenching her fists at her sides.

“I’m tired!” she shouted.

I shrank back like a scolded puppy. Nataki then stormed into the kitchen and grabbed a large blade from the knife block. I sat there, unsure what to do.

She became convinced that the apocalyptic rapture that many Christians believe to be foretold in certain scriptures had begun, and that she had been left behind with me and all the other hell-bound heathens.

Nataki stomped back into the room and raised the knife over her head. I fought a reflexive urge to lift my arms in self-defense, hoping to restore her trust in me with a reckless display of my trust in her. It didn’t work. As the knife came swooping down, instinct took over. My right hand shot out and knocked away the weapon before it could slice my throat. I jumped up and sprinted toward the front door, barefoot, snatching my keys from a wall-mounted metal rack as I passed, blood spewing from the flesh between my thumb and index finger.

Nataki was right on my heels, still wielding the knife, raving. We tore through the courtyard outside our building like predator and prey. A young couple appeared ahead of me, directly in my line of flight, their mouths falling open as they moved aside. I made two right turns, dashed across a parking lot, and scrambled into my aged and unreliable Ford Taurus. It took three tries to jab the key into the ignition switch. When the engine started, I looked up and saw Nataki running toward the car, looking intent on finishing the job.

I shifted into reverse and kicked the accelerator, going backward until I had clearance, then cranked the steering wheel to the left and screeched away. Having left my cell phone behind in the apartment, I drove to the nearest supermarket, where I dialed 911 from a pay phone.

“Please don’t take her to jail,” I begged the dispatcher. “She’s not a criminal. I think she’s sick!”

The responding officers came to the same conclusion, and Nataki spent the next 12 days in a psychiatric hospital, where she was diagnosed with bipolar disorder. I suppose this was bad news, but for me it came as a relief, because at least we now knew what we were dealing with. And the disorder was treatable. I couldn’t wait to get the old Nataki back.

In hindsight, I can only shake my head at my naivete. Ten long years would pass before Nataki gained lasting stability and our relationship arrived at its current happy equilibrium. Six more hospitalizations followed the first, each one preceded by another violent episode.

Our worst day came in 2007, when I found Nataki setting fire to one of her Christian books in the kitchen of our new home in California’s Central Valley, embittered about God’s failure to cure her mental illness. My clumsy efforts to manage the crisis served only to escalate it, and the next thing I knew, Nataki was coming at me with a seven-inch santoku. In the ensuing struggle, I struck her with a closed fist, not once but twice. These acts of self-preservation undoubtedly spared me from having my carotid artery sliced open, but they also earned me a night in county jail, accused of misdemeanor domestic battery. One of the arresting officers told me that they were mainly just trying to separate us, and the charge was later dropped. But the incident still made the local news, branding me as an abuser.

Even worse than such incidents, in some ways, were the lengthy periods when things were only a little off—when Nataki felt scared, confused, abandoned, and persecuted, and I felt powerless to help her. Make no mistake: Nataki had the worst of it. But for me, the unremitting worry was exhausting on every level. I thought about taking my own life almost daily, but the idea of leaving Nataki behind to struggle alone always brought me to my senses.

Throughout this long ordeal I kept running, more for the release it offered than to achieve big fitness goals. A funny thing happened, though, as I continued to train and compete: I became as mentally strong on the racecourse as I’d previously been weak. Once crippled by prerace nerves, I was now as relaxed on a marathon start line as I was in a supermarket checkout. When things got serious during the late stages of a race, I remained in control of my thoughts and emotions, making good decisions and always giving my best effort. In 2016, at 45, I won a 50K trail race, sealing the victory by overtaking a 31-year-old who’d recently run a 2:27 marathon—much faster than my 2:39 PR—in the closing miles. I simply outsuffered my younger, more talented competitor.

I thought about taking my own life almost daily, but the idea of leaving Nataki behind to struggle alone always brought me to my senses.

I’m certain that there’s a connection between the suffering I’ve endured at Nataki’s side and my transformation from a head case into an athlete whose head is his greatest asset. No matter how much pain I endure during a race, I’ve been through far worse in other contexts. Having managed not to quit on my favorite person, why in God’s name would I back off in a race just because my lungs are on fire?

One of the darker realities of endurance sports is that in order to be the best athlete you can be, you have to be really good at suffering, and one way to get really good at suffering is through experiences in your life outside of sports. A notable example is Frank Shorter, who won the 1972 Olympic marathon for the U.S. Subjected to appalling physical and emotional abuse as a child, Shorter later acknowledged that the cruelty may have made him a better runner, describing it this way in a 2011 Runner’s World interview: “What my childhood taught me was to be eternally vigilant. Vigilance evolves into consistency. I learned the solace of routine. I developed a way to ride my pain. ... I guess you could say that’s the perfect background for a marathoner.”

Psychologists have identified a link between traumatic experiences and inhibitory control, which is the ability to resist immediate impulses (such as avoiding fear or pain) and stay focused on a task or goal (such as supporting a loved one in need). Men and women who have experienced a certain amount of personal trauma tend to score better in measures of inhibitory control than people who have led relatively easy lives.

And you know who else does well in these tests? High-performing endurance athletes. In a 2015 study, Italian researchers observed that faster runners significantly outperformed slower runners in a standard test of inhibitory control. The following year, a different team of scientists reported a similar finding in cyclists.

I’m not suggesting that the athletic boost I seem to have gotten from domestic trauma made it all worthwhile. I wouldn’t wish our pain on anyone, not even from the perspective of the “happily ever after” that we enjoy today. But I am glad I was able to run through it.

It was another mutual friend of ours, Edith, who bailed me out of jail on the morning after I was arrested for battery in 2007. “I can’t imagine what you’re going through,” she said as she drove me home. Chewing on these words, I realized that the hopeless desperation I felt right then was not entirely unfamiliar. Indeed, I had felt something very much like it in races, specifically in those moments when I knew I was not going to make it to the finish line, having suffered too much to face the suffering ahead—those moments that came just before the moment I gave up.

The first thing I did after Edith dropped me off at my front door was to give in to my suicidal thoughts. I went into my closed garage, turned on my car, lowered the windows, and waited for the exhaust fumes to make my troubles go away. I blacked out. Some time later, I came to on my kitchen floor.

Being a runner doesn’t make life easier. But then, nothing really does.

What was it in my subconscious that stopped me from staying in that car—from quitting on life as I had previously quit in races? Without a doubt, my love for Nataki was the main factor, but there was also another. I believe deeply that I did not, in the end, take my own life because my athletic experience had changed me—strengthened me.

In the end, gaining the upper hand on bipolar disorder as a couple required nothing more and nothing less of both Nataki and me than simply hanging on. After her seventh hospitalization, in 2013, she began a new treatment regimen with a different set of medications. The combination has helped make the past several years our very best. She hasn’t had a major episode in the six years since.

It is often said that life is a marathon, but it’s perhaps equally true that a marathon is life—a condensed and simplified version of life that serves as a way to strengthen and prepare the mind for the greater struggle.

Being a runner doesn’t make life easier. But then, nothing really does. When it’s all said and done, there are no easy lives. Happiness, though, doesn’t come from having things easy; it comes from knowing your strength. When you’re strong and you know it, life’s wrong turns aren’t as scary. Through running we discover that strength, and it makes a hard life better.

Matt Fitzgerald is the author of Life Is a Marathon: A Memoir of Love and Endurance.