Not a chance, I thought. A year ago, the idea of me running a marathon was unthinkable. My responses to the notion were clear. I am not a runner. It’s boring. I am too old to start running and have no interest in running.

I refused to even consider running a marathon until a friend said something that changed my thinking and made me realize I had to try.

Exercise has been an important part of my life. I go to the gym several times a week, have a Peloton membership and enjoy yoga classes. People often ask how I find the time to make fitness a priority, and I share that there is no need to find the time; exercise creates time. Usually, this provokes a quizzical look, so I explain that for every hour of exercise, I get two to five hours back. The increased energy, mental clarity and emotional benefits of exercise go well beyond the time I invest in it. In business terms, exercise has a great ROI.

However, despite making a lifelong commitment to exercise, I have never been a runner. Running seemed excruciatingly boring. I didn’t think I was good at it, and when I did run, it felt like torture. Running 26.2 miles was unimaginable.

Then a friend told me I should listen to what I have been telling other people for the past 30 years.

The biggest thing that holds people back is themselves.

The most important key to success is the right mindset.

I had said things like this thousands of times, and now someone was using them on me.

Ouch.

After accepting that I was putting limitations on myself and realizing that running a marathon was something I could do if I believed in myself, I got to work. I found a marathon that was being run in October 2022, giving me nearly a year to prepare. I read several books on training and set a time goal. I usually set one big goal for myself each year, so running a marathon became this year’s goal.

I started training and progressed to a 13-mile run in two months. Then I suffered the first of four significant injuries. In early 2022, I had hip injury and adductor injuries that required me to stop running for nearly five months. It was a significant setback, but I was able ride a bike as I recovered, which helped. I started running again in June, but in no time I injured a toe, which required a minor surgical procedure. And shortly before the marathon, I pulled a calf muscle, making it impossible to train the two weeks before the race.

I was able to work through these injuries and trained during the sweltering Florida summer. And about a month before the marathon, I got Covid. I was in bed sick, not wanting to do anything, and training was inconceivable.

Despite the challenges and still not being 100 percent, I ran and finished a marathon Oct. 22. I had overcome some huge hurdles and reached my goal. I learned some big lessons during my training and race, and a few of them apply to all of us.

We hold ourselves back I was telling myself I could not run a marathon when I could. I have heard people share every reason imaginable why they could not reach their goals or achieve big things. People blame their failures on others or circumstances when the real reason they come up short is because of themselves. Some have said that a person’s saddest moment is at the end of their life, when God shows them who they could have been. If we don’t reach our potential, it is no one’s fault but our own.

Mindset matters A meeting in Washington, D.C., during my training created an opportunity to run through the capital. Though it was a hot and muggy August evening, the seven-mile run seemed like just a couple of miles because my focus was on the monuments, government buildings, including the White House, and tourists. My mind wasn’t focused on the pain of running; it was focused on other things, and it helped me. How we think affects what we can accomplish.

Don’t listen to the naysayers Not many people knew I was training for a marathon, but some who did thought I was crazy. They said I was too old, that it was dumb to train through the Florida summer, that four injuries should be a sign, and a bad case of Covid should keep me from running. I could have used these as excuses to step back from my goal. When you chase big things, people will give you reasons it can’t be done. Ignore them.

Have encouragers Thankfully, there was also a group of people, including my family, who encouraged me. It is essential to be around people who provide energy; it is because of them that I accomplished my goal.

Expect setbacks Aside from the injuries and Covid, Hurricane Ian hit Florida the week my training was supposed to peak. Great leaders get great results despite challenges. Don’t be surprised by setbacks; expect them. And achieve your goals despite them.

Tolerate discomfort After reading that the best runners tolerate discomfort, the idea of me tolerating, and even embracing, discomfort during my training was a game-changer. It again reinforced the importance of mindset. The best leaders do the difficult things, even when it is uncomfortable. (Expect more on this topic in a later column.)

After running the marathon, I am more convinced than ever that the No. 1 thing that holds us back from accomplishing big things is ourselves. Imagine the things you can accomplish if you believe in yourself. Is there something that seems impossible today that you could do with the right mindset? That would give you a great sense of accomplishment. What if you could stretch way outside your comfort zone? You can; almost everyone reading this article can accomplish more than they believe they can. What limits us? Ourselves.

Don’t hold yourself back. Live your best life; you get one chance. I have heard that on their deathbeds, people rarely regret things they did; however, they often have great regret about things they did not do. Don’t be that person; think of the things you want to accomplish and do them.

Bill Yeargin is CEO of Correct Craft and the author of five books, including the best seller Education of a CEO.