Diagnosed with Type 1 diabetes at age 22, the college student wasn't physically active to begin with and faced a choice — allow the disease to control his life or take charge of it himself.
"My first 'run' I think I ran for about 250 metres and that's all I could do," said Sasseville. "We all start from somewhere."
That somewhere would eventually take Sasseville, now 35, all the way across Canada after he completed a 9 1/2-month run on Friday to raise diabetes awareness and give hope to people living with the disease.
"It's not about running fast, it's not about running across Canada," Sasseville said after completing the trek of more than 7,500 kilometres on World Diabetes Day. "It's about making that first step and making that conscious decision that my life's going to be great, I want to set high goals, I want to pursue my dreams.
"The run is all about making that conscious choice, taking control, owning your disease and taking every necessary step to manage it properly."
It's estimated 300,000 Canadians have Type 1 diabetes, which results from the body's immune system destroying the insulin-producing cells in the pancreas. With little or no natural insulin, the body can't regulate how it uses and stores sugar, meaning injections are needed several times a day to prevent a buildup of sugar in the bloodstream.
"I've learned so much this year. Overcoming Type 1 diabetes is all about overcoming obstacles," said Sasseville, who lives in Quebec City. "That's the message I wanted to get across — get up, work hard, set high goals, don't give up and live a life that's inspired."
Type 1 diabetes differs from the more common Type 2 form in which the body becomes resistant to insulin or the pancreas doesn't produce enough of the hormone.
"Three million people in Canada live with a form of diabetes," said Sasseville. "It's an important day and I really hope that people who live with diabetes across Canada will be inspired by the run."
Sasseville was greeted in Vancouver's Stanley Park by a throng of screaming school children and supporters, including his parents, girlfriend and sister.
"I could have never dreamed of running across Canada 10 years ago," said Sasseville, his feet still wet after walking into English Bay. "To have done it that way where the whole focus was on a cause, on a message — not necessarily on a guy running — that was a blessing."
Also in attendance was Patrick St. Martin, Sasseville's best friend and driver who lived with the runner in an RV ever since the pair left St. John's, N.L., on Feb. 2.
"To see the impact we can have on kids, on people, it's just amazing. We're all overwhelmed with what is happening right now," said St. Martin. "It's 9 1/2 months on the road. Canada's a long country. There were obviously times when we would feel a little bit lonely, but events like (Friday) and meeting people, it's just crazy. It's amazing how powerful it is and how impactful the run is on people."
The duo said they remain close after all that time together, adding there wasn't a single argument while on the road.
"We had some hard days, of course," said Sasseville. "It's 180 marathons that you run on sore legs ... some doubts, some tough days, but that's when it really counts. Discipline only counts when you don't feel like going for a run."
Added St. Martin: "We had one goal in mind (and) it was to inspire people. I think that was what drove us to do it the right way."
Sasseville took part in dozens of events across the country, but it was a boy from Windsor, Ont., who left him with a lasting impression.
Jack Poisson, who also has Type 1 diabetes, met Sasseville when he came to town and the pair kept in touch by phone throughout the run.
"He was such an intelligent kid and very inspiring himself," said Sasseville. "I think Jack represents a whole generation of kids living with Type 1 diabetes that are hoping to live a full life. (They) may have doubts and fears, but I think with events like the run across Canada, if we can get to them and let them know 'Hey you're going to be able to live the life you want,' that's cool."
Poisson — who took his support of Sasseville even further, raising more than $2,700 by asking for donations instead of birthday presents and also fundraising at his school — was at the finish line with his family to cheer on his hero.
"It's my first time in Vancouver," said Poisson. "It really means a lot to me because I get to see one of my good friends finish running across Canada."
Sasseville has also taken part in Ironman events, raced across the Sahara Desert and was the first Canadian with Type 1 diabetes to reach the summit of Mount Everest, but accomplishing this feat intrigued him.
"I found running across Canada very interesting," he said. "I knew there would be a lot of challenges with that, but that was the pull. You always learn great stuff when you give yourself the gift of maybe failing."
Sasseville said the feeling he had Friday was better than the one experienced after conquering Mount Everest in 2008.
"Mount Everest is all about you. You get to the top and it's a personal achievement," he said. "Whereas ... that feeling of having built something and having thousands of people being a part of it — that is priceless."
For a man who seems set on pushing his limits, Sasseville is content to relax — at least for a little while.
"Rest, sleep, steak," he said of the comforts he missed while on road. "It's all the little things. I miss a warm shower that lasts more than five minutes."