HALIFAX - With his arms outstretched, Josh Cassidy can barely hold up the dozens of medals he has amassed over the years.

But despite holding the world record for fastest marathon in a wheelchair, Cassidy knows a medal is missing.

"You don't get the medals for the quote-unquote failures," he recently told a room of young wheelchair athletes in Halifax. "The ones that you don't win, those are the ones where you learn the most."

Cassidy is gearing up for a comeback at the Rio Paralympics this summer after a disappointing finish in at the London Games.

At the 2012 Boston Marathon, the Ottawa native set a wheelchair marathon record of one hour 18 minutes 25 seconds, a full 12 minutes quicker than the first-place time at the London Paralympics four months later.

The victory sent Cassidy to London with lofty expectations. But if Boston was the high point of his season, the Paralympics were the opposite. Struck by a mysterious flu, Cassidy came fifth in the 800 metres, 10th in the 1,500 and 12th in the marathon at the Games.

"Despite that disappointment, it taught me how to let go," Cassidy said in an interview. "That one week didn't define me. It was everything I had done for the previous years leading up."

He has since purchased a new racing chair, seen a sports psychologist and taken on a gruelling twice-daily training regimen. It will cost Cassidy more than $70,000 to train for this year's Games, and he is staking his financial future on winning sponsorships.

Just one more challenge, said the 31-year-old who has spent his life overcoming obstacles.

"Sports is such a microcosm of life," Cassidy said. "Those tools can be applied to other life obstacles ... Not looking at our shortcomings and our failures as failures, but as opportunities to expand ourselves."

Weeks after birth, Cassidy was diagnosed with neuroblastoma, a cancer of the spine and stomach that left his legs partially paralyzed.

"It may be a controversial thing to say, but the cancer I had ... was the best thing that ever happened to me," he says. "It helped me a such an early age to learn how to adapt."

Cassidy's racing career began in high school. He quickly dominated the Canadian scene, sweeping up four national wheelchair records, from the 1,500 metres to the 42.195-kilometre marathon, and won road races around the world.

A week after his historic win in Boston, Cassidy set his sights on the 2012 London Marathon. He dedicated the race to five-year-old Niamh Curry, who was battling the same rare childhood cancer that struck Cassidy as an infant.

It was the first time Cassidy had been nervous for a race. He didn't sleep the night before the marathon and ended up placing eighth.

"I know I put so much pressure on myself that it was up to me to make the difference," he says. "I just so deeply within me wanted to see (Niamh) healthy and happy."

Cassidy crossed the London finish line backward to show off the photo of Niamh he wore on the back of his racing shirt. The little girl from Northampton, England, was supposed to be there at the finish line but her health had taken a turn for the worse. She died a couple of years later.

Following his 2012 disappointments, Cassidy has been on a steady but uncertain trajectory back to first-place.

Cassidy was in Boston to defend his title in 2013, when he heard explosions at the marathon's finish line. He was uninjured, but says he felt the city's loss.

As an Ontario native, the pressure was on for him to perform in last summer's Parapan Am games in Toronto, where he won three silver medals.

Now Cassidy is focused on finally making a trip to the Paralympic podium in August.

"My goal for Rio is the medal that I'm missing for the Paralympic games," he said.

News from © The Canadian Press, 2016