It is the day before my fifth chemotherapy treatment and I am in a quandary.  I want to go for a long run, but I’m not sure I have enough time to recover before my drug infusion the next day.  I've failed to get out early; if I run, it would be at 5 p.m., leaving less than 24 hours before the treatment starts. But it’s sunny and 70 degrees, a beautiful spring day.  How can I not go?

I choose a longer route than I’ve run in a few years, seven miles, mostly through the mature woods of a Washington, D.C. park. The trees soak up the stress of bouncing emotionally from treatment to treatment better than any spa could. There is no better fragrance than the woods in early spring, and no better way to inhale it than to breathe deeply in full stride.

I grow tired toward the end, but the steroids I’m taking as part of my regimen help power me through. My not-exactly-blistering pace is just over nine minutes a mile, but I finish the whole run.

The treatment the next day is a bit rougher than usual. That's to be expected. The side-effects of chemotherapy are cumulative. This time I experience more nausea, sleeplessness and anxiety. But the run provides a memory that stays with me throughout the week.

I am 46 years old, married with an 8-year old daughter, and a nice career as a writer and communications consultant. My cancer is early stage lymphoma and I'm now finished with all six chemotherapy treatments.  Since February, I've spent a week and a half recovering from each one. Then I've run every other day for the next week and a half.  It’s the first running rhythm I’ve established in years. My prognosis is good; I hope to get the “all clear” from my oncologist soon.

I started running in high school. Even though I was a sprinter on the track team, long-distance runs were a core part of the training regimen. I kept running as I grew up. It's a time to work out personal problems, think creatively, push past barriers. To cope with what life throws at me.

The most memorable run of my life took place about seven years ago, on the day my younger brother died at age 34 after a lifelong struggle with kidney disease. I ran about four and a half miles that morning. It wasn’t a challenging route and I didn’t go very fast.  It was a nice spring morning, birds singing and flowers starting to bloom.

Later that day, after my sister-in-law agreed to take my brother off life support, my daughter also went for a run. We say that she started walking that day, but the truth is, it was more of a lurching run. She stumbled 15 feet, back and forth between her aunt and me, delighting in the movement and the joy she brought to that terrible day. Running, to me, has always been like that--an act of physicality that brings peace.

I relived those moments on my seven-miler. Running has always been in my core, something that defines me and comforts me in good times and bleak moments. But that spring seven years ago was the last time I had run consistently. Since then, my routine has been de-railed, first by parenthood, then by the near constant demands of earning a living.

Now cancer and chemotherapy, of all things, have given me back the gift of running.

At the start of treatment, I was assured that I could run. “No problem,” the medical staff told me, “many of our patients run, swim, play golf, ride bicycles.” Easier said than done. Running is much harder on the body than those activities.

In order to receive chemotherapy drugs, I have a catheter that was implanted in my jugular vein. Its “port”--a titanium top to the catheter--is a visible bump in my chest.  It took me a while to heal from the surgery to install this hardware, and more time to get used to running with the new gear inside of me.

The first run after treatment always feels horrible, like I haven’t run in seven years. By the second or third I’ve recovered enough to move fluidly--never crisply or with great speed, but after a finishing kick I leap high to smack the top of a stop sign, which responds with a reassuring clang.

My daughter has begun saying she wants to run with me. I want to make that happen, but not until I am through the last treatment and its aftershocks.  She is already athletic, into gymnastics and soccer. She is lithe and strong, and like me, so happy when her body is moving fast.

I've never had company on a run. I had never been willing to adjust my routine to accommodate others, even my wife. And I've always worried that it will be less rewarding to run slowly.

Now, however, I feel ready to make exceptions.  I would love to watch my daughter grow into her own exercise habit, one that sees her through her own life’s struggles. Setting the example for her as I go off on my runs is important. But traveling that route with her would be running's greatest gift so far.

Dan Klotz has run the Empire State Building race four times, the last time more than 10 years ago. He is looking forward to his fifth chance in 2015.