This month, I completed my second Spartan Race up in Tuxedo Park, NY. I was part of an amazing team, including my dear friend Linda, who taught me a powerful lesson on the Slippery Wall.

Linda was my sorority “big sister,” but we lost touch after college until a few months ago. We reconnected through Facebook, which was how I got involved in the Spartan race in the first place. She’s a lawyer here in New York, and when we met up last fall, she was still wearing a head scarf from her second round of chemo for breast cancer. After her first round, she told me, she’d thought she was done with cancer. So when it came back again, it shook her to her core.

I have to live my life, she realized. I have to get out there, have fun, be with people. I have to step outside my comfort zone, and go for the things I really want.

One of those things was the Spartan Race, a couple weeks ago.

One of the obstacles was the Slippery Wall, a slanted wall that you had to...