(Li Zhongfei/Istockphoto)

Four months after my husband of 12 years moved states away, I clocked 60 miles in a single January on a treadmill at the only local gym I could find that offered child care. I’d tried running before, but anytime I pushed past the three-mile mark, an arthritic pain gripped my right knee. I was black and blue on the inside, a brand new solo parent with a toddler and kindergartner. I needed to run.

I’d grieved once before, when my only sibling killed himself just after I married. Although he broke my heart, I understood: He was nearing 30, things hadn’t turned out the way he’d expected, so he quit. At that time in my life, I had the luxury of falling apart. I drank too much, stayed up late listening to music, cried when I wanted and left the house for hours on a whim.

This time, two tiny humans depended on me for strength, love and comfort. I couldn’t fall apart, so I ran. The motion calmed me, like rocking soothes a baby. I couldn’t stop the pain the divorce caused, but I could set out to run a certain number of miles each day and then do it. Running took the edge off hurtful text messages, excruciating silences and the empty side of the bed I couldn’t bring myself to claim. It was the perfect antidote to parenting young children. When I ran, I was free to move as fast as I could. No one stood in my way but me. Self control brought me closer to self trust, one step at a time.

I aimed for a half-marathon first. I knew it would take slow progress and medical help to get me past three-mile runs with my bunk knee. My chiropractor noticed one leg was shorter than the other; my left hip sunk too deeply in its socket. I performed daily therapy exercises, had my back cracked and saw a sports massage therapist who gave me advice I most needed to hear.

“You’re not broken,” he said. “You’re just stuck.” He smiled and targeted a knot in my lower back, forcing it to release.

That summer, I ran my first half-marathon while the kids stayed at my friend Sunshine’s house. No one came to meet me at the finish line. Perhaps it’s the lesson I needed: You’re in this by yourself. Single. Solo. Alone.

The next summer, I completed my first full marathon on my daughter’s fifth birthday, crossing the finish line to drive myself home.

This past July, I attempted my second marathon. My secret hope was to beat my time from the previous year: I’d finished in 4:08. After training hard all spring, I found a spot near the starting line within sight of the 4:00 pacing group on a perfectly cool morning. The first time I ran this race, I needed to prove to myself that I could go the distance. This time I hoped to do it with skill and strength, to find a new best.

I passed my pacing group easily in the first mile. I took care not to spend my energy too soon, but my training made me confident I hold the brisk pace. I no longer felt broken or stuck. I felt strong, prepared, better than ever.

Until Mile 5. That familiar tightening seized my right knee — a pain I’d spent three years eradicating. For an entire mile I processed a single, circular thought: Is that my knee? No. It’s just a glitch. I’m just settling in. But wait. That is my knee. Is that my hip? And my knee?

My left hip started hurting as well. I knew enough about biomechanics to understand my pelvis was out of line, causing this ping-pong kind of pain in opposing joints. I fell back in with the 4:00 pacing group, hoping that slowing down would give me a chance to recover. After all, I still had 20 miles to go.

I have a pretty high pain tolerance, as much as anyone can be sure of such a thing. I birthed two children naturally, and I reach for ibuprofen rarely enough that my ex-husband used to jokingly ask on such occasions whether I might need a ride to the emergency room. As I neared Mile 10, I thought about my first birth (the longer, more painful one), my knee and hip now barking fiercely with each step: Stop, stop, stop.

By Mile 15, I took a walking break and gazed up at the sky to keep tears from spilling over. My pacing group vanished over a hill. I’d worked closely with my doctors, so I knew running on the angry joints would not cause permanent damage. I’d have to take a couple of weeks off to calm the inflammation and correct my alignment. Although I went into the marathon deeply anxious that I might not achieve my ideal time, I never dreamed that I’d have to walk part of the way. Or, even worse, that on Mile 16 I’d contemplate quitting.

As I walked, I thought about what it meant to quit. I thought about my kids waiting to high-five me in my friend’s yard at Mile 22. I thought about the past three years, about everything I’d run through to get here. Between myself and the kids, I’d run through 11 earaches, nine rounds of stomach flu and a dozens chest colds. I’d run on the December morning before a judge restored my maiden name and declared me unmarried. I’d run through the dizzying labyrinth of 21st-century dating, through depression, shame and doubt. I’d run through my ex-husband accepting literary awards in faraway cities and vacationing with his girlfriend (a decade my junior). I’d run through three moves, 15 lost teeth, the ebb and flow of freelance work, parent-teacher conferences, through wind and rain and heat and snow. Now this? This pain like broken glass in my knee and hip? I’d run through this, too.

On Mile 18, as the 4:10 pacing group passed me, I found hope. In my mind, I’d been hours instead of minutes past my goal finishing time. But 4:10 was a solid time; 4:10 meant I had a chance. I wiped away tears and ran after them. I noticed that walking for even two minutes earned me a stretch of less painful running. Sometimes I passed the group, sometimes I walked while they passed me. As I ran by a group of cheering spectators, I looked behind me to see whom they were rooting for. When I realized it was me, I started crying. I ran a little faster.

You’re not broken, just stuck.

Around Mile 20, I realized how close I was. I can run six miles with my daughter on my back, I thought. I can run six naked and barefoot. I can run six with closed eyes. I picked up my pace and didn’t stop until Mile 22. I’d texted my best friend to pass off my knee brace when I reached her front yard, and to warn the kids that I might be a mess. When I saw Sunshine heading toward me with the brace, my face crumpled. I kissed my son and daughter and mumbled a few words before dashing off.

Those last four miles might be the fastest stretch I’ve ever run. The brace and endorphins eased my pain. I cranked my power music and sang along. I ran like I was born to do it. I ran the way I’d meant to.

As I came over the bridge that marks the end of the race, I broke into a sprint. A large group blocked the entire marathon lane, so I jumped the median, passed them on the half-marathon side and jumped back in time to miss the barricade that divided the finish lines. I was stunned to see I pulled in a 4:12 — only four minutes off from my finish the previous year.

Although just an hour earlier I swore I’d never run a marathon again, already I wondered what kind of time I’d be capable of if my knee and hip held up next time. I’d crossed that line alone again. It didn’t matter — I’d done it for myself, but not by myself. The cheers and encouragement pushed me forward the same way the kindness of friends and strangers had helped me through the divorce.

I never wanted to be divorced, an only child or a single mom. And I know my children will one day have to reckon with some hard memories. My highest hope is that among whatever difficult snippets they retain — my voice raised, their father gone, a need unmet — they also remember me on Mile 22, leaning over to strap on a knee brace and kiss their perfect little heads, telling them through sweat and tears (for better or worse), “This is what not quitting looks like.”

Because on the other side of not quitting is thriving, but you have to not quit to get there. You have to have faith.