Lleyton Edwards went through a "rollercoaster of emotions" seeing his best mate lose his life at age 20.
Lleyton, of The Hill in Newcastle, said it seemed harder "being a long way away, almost feeling helpless".
"There's not a lot I could do from the other side of the world, apart from maybe take his mind off it," he said.
Luke Bailey lost his fight with blood cancer in August last year.
He had a bone marrow transplant to treat leukaemia, but died after developing a severe immune reaction called graft versus host disease.
To mark the anniversary of Luke's death, Lleyton set himself a mammoth challenge - running 1000 kilometres in 20 days - to raise money for the Leukaemia Foundation.
He's been running a circuit five times a day - covering 50 kilometres - from Nobbys to Throsby Creek Bridge to Newcastle Baths.
Injury, though, has forced him to take rest days.
"Obviously I didnt want to stop, but it's better than stopping the whole thing."
He's determined to meet the 1000-kilometre target.
"You face adversity and you've got to overcome it," he said.
Lleyton and Luke met in England, having known each other since they were babies.
"Our parents were friends before we were born," Lleyton said.
When Lleyton moved to Australia nine years ago, the pair remained close.
"Losing my friend at such a young age made me realise life is really short," he said.
"I want to push myself to the limits and do these things for those who can't.
"I want to make sure I live life the way I want to, so I can look back one day with no regrets."
Luke inspired him.
"He never complained about what he was going through. We would talk on the phone or play Xbox together.
"It was incredible how someone going through such a difficult time at such a young age could remain so positive and be a beam of light."
Lleyton, an apprentice landscaper, began running at age 18 to stay in shape.
"I got a bit overweight after I finished high school. I was free, drinking a lot, living at home, not paying rent and living for the weekend.
"I had bad habits. During the lockdown in 2021, I decided I'd change and stay consistent with it."
Last year, he did two triathlons, a half marathon and a marathon.
"Running is definitely therapy for me," he said.
It helped him cope with depression, which he's had since age 16, and grief from Luke's death.
Leukaemia Foundation chief executive Chris Tanti said fundraisers like Lleyton help support the 53 Australians diagnosed with blood cancer each day.
Mr Tanti said the foundation provided patients with services, so they can "concentrate on getting through treatment and surviving their diagnosis".
The foundation, which also invests in research, said about one in 12 Australians will be diagnosed with blood cancer in their lifetime.
So far, Lleyton has raised about $9000. Support his cause at fundraise.leukaemia.org.au.
