(CNN) -- A little more than two months ago, I stood on a California beach, tears streaming down my cheeks as I watched members of the 2012 CNN Fit Nation team cross the finish line of the Nautica Malibu Triathlon.
A year before they had never worn a pair of running shoes, let alone a triathlon suit. For many of them completing a triathlon was utterly inconceivable, akin to asking them to walk on the moon. But what a difference a year made.
At the Nautica Malibu Triathlon, I saw the Lucky Seven athletes conquer their fears and achieve more than they could have ever imagined. Their courage, strength, happiness, elation and pride were a beacon that shone for all to see, and that light continues to inspire everyone who shared in their amazing journey.
It was an absolute privilege to join Dr. Sanjay Gupta and Coach April as a guest coach for the 2012 CNN Fit Nation team. The finish line was not the end for the Lucky Seven; it was just the beginning.
Their journey did not simply bring newfound physical fitness and vigor. The experience gave the team members altered perspective, a sense of purpose, healthy eating habits, a wealth of new skills, mental fortitude and a string of wonderful memories.
It gave them a new life as triathletes, filled with belief in themselves and lifelong friendships.
Of course, challenges are never easy. It takes a huge amount of courage to try a new sport and set a new goal.
The Lucky Seven all had personal barriers. They were all nervous about testing themselves, taking risks and biting off more than they could chew. They all worried about the what ifs. What if I can't do the training? What if I can't learn to swim? What if I crash on the bike? What if I can't finish? What if I let myself down?
While watching them conquer their fears, I realized once again that the only limits are those that exist in the mind. The key is to overcome and move beyond them -- to a space where our real power dwells.
Four years ago I was asked whether I would ever do an Ironman. My response? "No way, you must be completely mad to do something like that!"
But once I had done the shorter distance races, I realized that maybe the Ironman mountain wasn't so big after all. I gained confidence in myself, and with the support of my coach and training partners, I seized this new, exciting challenge with both hands.
Imagine if I had never gone back on my word, if I hadn't changed "I can't" to "I can." Imagine if I hadn't dared to push myself harder, and most importantly, if I hadn't had people to support, encourage, mentor and make me believe in me? I would never be sitting here as four-time Ironman World champion.
The same goes for the 2012 CNN Fit Nation Team. If the team members hadn't had the courage to overcome their fears and doubts, they may never have been able to call themselves triathletes. And they, and their families and loved ones, may not be looking to the future filled with optimism, positivity and unbridled confidence.
I await the news of the selection of the 2013 CNN Fit Nation team, knowing it marks the start of a journey that will change lives, empowering a new group to defy what they may have deemed impossible and inspire everyone else out there to do the same.
This is the start of a new beginning, for them and for you.
To apply to be a 2013 CNN Fit Nation team member, go to iReport.com and share your story. If you are selected, you'll receive a bike, uniform, wet suit, personal training and nutrition coaching, two all-expenses-paid training trips and a chance to train and compete alongside Gupta at the 2013 Nautica Malibu Triathlon.