I am not a  runner. Stamina is not my thing. Nonetheless, on the morning of the first investor pitch for our startup, I went for a run.

"Just three miles," I thought. Maybe I needed to clear my head. Maybe I wanted to purge my body of sweat, so the beads wouldn't drip down my face in front of millionaires. Maybe I wanted to experience  failure so I could recognize it later.

Earbuds in, I huffed my first big gulp of air after a quarter of a mile. I was aware of the mythical place where your body was used to running, but I had never found it. The place runners call their 'numb point,' when you find your stride, your breathing becomes rhythmic and your gait consistent, and you feel like you can run forever. A half-mile in to this particular run, that moment felt as far away from me as it ever had. Which made what happened next even more surprising.

The song changed. Now the cadence of "I'm Amazed" by My Morning Jacket matched my steps perfectly. In that moment, I lost myself in running. I wasn't thinking about physical exhaustion, jiggly quads or impending defeat. I was asking myself questions:

"Who can I help today?"

"During the pitch, will I face questions I'm unprepared to answer?"

"Am I running faster than the lady coming toward me?"

I'd found my numb point. And then--BAM! A pain in my calf so sharp, I swore I'd been shot.

I collapsed to the pavement. Both hands squeezed my calf as I rolled in agony. I peered down at the zone of pain. I lifted my fingers one by one. No blood. No bullet hole.

"Impossible!" I thought. I expected nothing less than a combat wound from such acute pain. Attempting to stand, I couldn't put weight on it. The muscle was pulled.

"Well, no one could run with this injury," I told myself. "I've already run what, a mile? There's no shame in limping home." "Kudos for the attempt Matt, good on ya, sorry about the bullet, err...pulled muscle." I paused, breathing heavily, and a thought beyond a phantom bullet struck me: "Am I expected to fail?"

Entrepreneurship may seem like the new black, but statistics about the high rate of startup failure are staggering. Analyzing 10 years of its own investments, respected early-stage venture fund First Round Capital correlated 10 factors with success. Among them: an Ivy League education (including MIT/Stanford), a previous high-profile employer, and youth.

As I stood favoring my injured leg, those factors bounced around my mind. I neither attended an Ivy nor apprenticed at Google, Facebook or Amazon. And it's been a while since I was 25. So maybe I shouldn't bother?

A pulled calf muscle was giving me the excuse I needed to make failure acceptable. "If I can't finish this run," I thought, "in which the only obstacles are a seldom-used diaphragm and a painful calf injury, why should anyone invest in me?"

I winced through a few steps, started to walk, then at some point I found myself running again. Half a mile later, my numb point returned.

When I finished the run, I flopped down with gusto on my concrete driveway. Anguished screams brought my wife and our two-year-old son out to find me clutching my leg. Peering down at me, she asked in the sweet brogue only I notice, "Um, so how are you doing then?" Looking her square in the eye, I said, "I feel awesome."

I am not a runner. I had set out to run three miles, and--after pulling that calf muscle early--ended up running six. I popped some ibuprofen and limped into the office.

As a founder, some days you crush it, and some days you're crushed. Some days both happen within minutes. A phone call brings celebratory cartwheels, and then a video chat makes your heart skip a beat. Keeping a cadence is the true challenge.

Anything can throw you off rhythm. Investors may say they believe in a balanced life, while you know they secretly hope you work weekends. "Good morning" may be all you have time to say to your family for several days. A deal that could put you over the top may take forever to close.

When adversity strikes, if you can find a way to keep running, you may reach a point where you'll feel like you can run forever.