Kenny Logan's battle with prostate cancer made the former Scottish rugby star realise "how fragile life can be".
But as he told AFP, at least a cure is available for his condition whereas none exists for Motor Neurone Disease (MND), which claimed the life of his former teammate Doddie Weir last year.
Logan has enlisted stars of sport and the silver screen including former Scotland striker Ally McCoist and award-winning actor James Nesbitt to take on a daunting 700-mile challenge to raise £555,555 ($680,000) for Logan's "true friend" Weir's charity, My Name'5 Doddie Foundation.
It is a daily mix of walking and cycling, over seven days, beginning in Edinburgh on Sunday week and arriving at the Stade de France with the match ball for the kick-off of Scotland's Rugby World Cup game with Ireland on October 7.
The hugely popular Weir, who was capped 61 times from 1990 to 2000, died aged 52 last November having lived with MND for six years.
Logan, who made 70 appearances for Scotland from 1992-2003, often playing with second rower Weir, was given the all clear for his cancer in February, almost a year after being diagnosed.
"My own health scare made me realise how fragile life can be," Logan said in an interview with AFP.
"I was lucky to get the all-clear, and I'm really thankful for that.
"But it also showed me the huge difference between my situation, which could be treated, and Doddie's battle with MND, which has no cure.
"That's why we're so determined on this journey.
"Every pound we raise makes a real impact in the search for a cure, and our ultimate goal is a world free of MND."
Logan says Weir's courage and stoicism were extraordinary.
"Doddie was more than a teammate; he was a true friend and a man full of positive energy, both on and off the pitch," said Logan.
"We had our share of fun and laughter, but he also had a serious side.
"Even when he received that devastating diagnosis, his character continued to shine through.
"Doddie's courage and bravery are unmatched; I've never known a man with more of both."
- 'Devastating disease' -
Logan, who says they have raised £210,000 of the target, has not lost his sense of derring do and it was he who decided to make the trip even more challenging.
"The idea for this epic journey started with a simple thought -– let's do something extraordinary to support the My Name'5 Doddie Foundation," he said.
"Originally, I planned to walk the entire way from Edinburgh to Paris, but then I thought, why not make it even more challenging?
"I knew that cycling was a popular choice, but no one had ever combined cycling and walking.
"So, we decided to do just that and create something unique."
Logan says it was "heartwarming" how the others immediately accepted the change in plan.
The "most daunting part", he said, was stepping into the "unknown" on the first day.
For Nesbitt, who has starred in films including "Bloody Sunday" and "The Hobbit" series, it was "a privilege to say yes."
"Through my work with the foundation I'm aware of just how horrific the disease is, which is why it's so important for me to take on the challenge," he told AFP.
Nesbitt, who used to have shares in racehorses and has encouraged many of his racing contacts to contribute, has been "really getting into his training", according to Logan.
"Cycling from Belfast to my house in Portrush, which is 107 kilometres, was the longest I've managed and tough going but very rewarding," said the 58-year-old Northern Irishman.
Logan admits "keeping MND and Doddie's charity in the spotlight is indeed a challenge" but he will not let up in his efforts to keep the flame burning.
"It's about keeping their name and mission at the forefront of people's minds," he said.
"Together, we can make a lasting impact in the battle against this devastating disease."
The camaraderie, though, only goes so far once they are settled in the Stade de France.
"Come kick off, Kenny is no friend of mine!" joked lifelong rugby fan Nesbitt.
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