Jim Rohn made an notable observation when he said, “Character isn’t something you were born with and can’t change, like fingerprints. It’s something you weren’t born with and must take responsibility for forming.”

It’s interesting because many people seem to think that character is built-in; either you won the character lottery or you didn’t. But Rohn’s right—a good character is a habit that’s formed by consistently making the right choice for the right reasons.

But that doesn’t mean that we don’t all have a little help. Each of us has our own strengths and, when we push ourselves to discover them, we often learn that they can be quite useful for building character.

When I was in the military, I took a performance test that was disguised as an advanced training course. The test was designed to weed out the best people to pursue a new career in diving. It was an impossibly strenuous course, and we operated on little to no sleep and limited nourishment. We were up at all hours of the day and night–running, swimming, and working out. It was an emotionally challenging time, and we were all forced to push ourselves to our limits, physically and mentally. Now here’s the catch: the course didn’t end until we were down to just six people. The longest record was 21 days.

Everyone was given a whistle, and when they were at their breaking point, they blew it to indicate that they were giving up. I had some tough competition—each of the twenty participants were at the top of their current line of work, whether they were medics, infantrymen, or search-and-rescue technicians. But still, it wasn’t long before we were down to nine.

After all, it was easy to quit. If you weren’t in the top six, nothing bad would happen to you. You just went back to your current high-level career. But if you won… you got to move on to a new diving career with a new mission. You’d be taking your career to the next level. And it was all up to you.

The night the test ended was also the night I encountered one of the hardest challenges I’ve ever endured. That night, we were woken up for a run after only an hour and a half of sleep. We were asked to bring our diving gear along with us.

We ran and ran. We passed all of our usual landmarks and kept running. It felt like we were never going to stop. I knew I didn’t have much left in me, so I started playing mind games, telling myself to run to the next landmark before giving up. Then, when I hit the next landmark, I’d set myself up for a new challenge.

Finally, we hit the water, and without letting us stop to rest, the instructors told us to suit up and start swimming. At that point, I really knew I was done. But then I heard a whistle. We were down to eight!

There were only two of us left to quit, but I decided to try and push through until one more person whistled. When they did, I was almost ecstatic. I’d be done soon! It was my turn!

Just when I was about to blow my whistle, someone else beat me to it. The challenge was over, and I was in the top six. There were just seconds between winning and losing, but I kept persevering, and in the end, it paid off. We were finally done, after 19 long days.

Staying true to my character and testing my limits allowed me to take a step in my career that I almost missed out on. Has there ever been a time when perseverance changed your life? I’d love to read about your experiences in the comments below.