Born without a left foot, Mr Shariff Abdullah had his left limb amputated below the knee in 2008 because of a skin infection. Three months later, he took up running and, since then, has completed nearly 25 marathons, including the Boston Marathon.
But one race eludes him - the gruelling Tenzing-Hillary Everest Marathon. Known as the world's highest marathon, it begins at 5,184m above sea level close to Everest Base Camp in Nepal, before taking the runner though 42km of rough mountain trails.
The 47-year-old inspirational speaker, who called off his attempt last year because of the Nepal earthquake, tried again last month. He trekked about 65km from Lukla in Nepal to the starting point of the marathon, but the tough conditions forced him to turn back. He had hoped to raise $5,000 for the Club Rainbow charity through the run.
Still, his daughter could not be more proud. "I feel happy that my father did this for me," said 16-year- old Nur Athirah Md Shariff Abdullah.
Since she was a baby, she has been living with liver cirrhosis, a disease that slowly prevents the liver from functioning properly.
Club Rainbow is a voluntary organisation that helps chronically ill children and their families. Started in 1991 as a camp for children with various chronic and life-threatening illnesses, it offers services and help through counselling, social activities and financial aid.
Now helping more than 740 beneficiaries, it is looking to increase the number of beneficiaries to 1,000 by 2019.
Apart from donations from corporate organisations, Club Rainbow is also helped by fund-raising efforts of parents of beneficiaries.
To raise awareness and show support for its beneficiaries, the club also organises various public volunteer events throughout the year. On July 24, it will hold its flagship cycling and fundraising event, Ride for Rainbows, for the fifth year. Volunteers will cycle along the streets of Singapore to show solidarity and support for the children.
"With the help of the volunteers and staff, hundreds of children, whose lives are filled with challenges and difficulties, are able to see a light at the end of the tunnel," said Dr Sashikumar Ganapathy, the club's president, in a message on the Club Rainbow website.
Her condition can cause complications such as reduced oxygen in the blood, increased risk of infection, excessive bleeding and bruising and, in serious cases, kidney failure. She had to take a year off from school recently due to her condition, and goes for monthly check-ups at KK Women's and Children's Hospital.
"Sometimes, I get scared when I have to go to the hospital, but I know that my father will always support me," said Athirah.
The Secondary 4 student from NorthLight School is also part of Club Rainbow, which helps children suffering from chronic and life-threatening illnesses.
To help Athirah, her family - including her mother Rozana Shariff, 54, and siblings Nur Anisaa, 21, and Nur Atiqah, 23 - makes sure there is always someone at home with her. Ms Atiqah is studying graphic design at the Nanyang Academy of Fine Arts (Nafa), while working part-time as a sales assistant.
She is close to Athirah and often takes time off from her busy schedule to take care of her when she falls ill. Athirah wants to follow in her big sister's footsteps and study at Nafa.
Mr Shariff said: "As a father, all I can do is to tell Athirah to be positive. I want her to be happy and to be able to do what she loves in the future. Although she is sick, and goes through so much hardship, she's just like any other teenager.
"She loves K-pop and Korean dramas and she has goals and dreams just like everyone else."
He was told originally that his daughter had leukaemia.
He said: "Knowing that this isn't the worst case for her, I already feel grateful. The best Father's Day present would simply be her love and happiness."
As for his attempt at the Everest marathon, he said: "My daughter was my biggest motivation. When I was up in the mountains, all I could think about was making her proud.
"Everything I do, I do for her."