Makaziwe Mandela told South Africa television that the country's former president is "still with us, strong, courageous".
"Even for a lack of a better word... on his deathbed he is teaching us lessons - lessons in patience, in love, lessons of tolerance," she added.
She went on: "Every moment, every minute with my father amazes me and there are times when I have to pinch myself that I come from this man who is so strong, who is a fighter."
Since September the 95-year-old has been treated at home after spending several months in hospital.
South Africans have been expecting the worst since June when the leader was admitted with a recurring infection thought to stem from his years of incaceration. Much of his time in prison was spent on Robben Island, where he did hard labour breaking rocks.
In July, his wife Graça Machel broke her vigil by his bedside to say he was "fine" although still uncomfortable. She added: "The best gift that he has given is the gift of unity."
Celebrities around the world sent their best wishes, among them the Clintons, David Beckham and Lewis Hamilton. Naomi Campbell, who describes him as her honorary grandfather, said she was in constant touch with his family.
Many tweets referred to him as Madiba, his clan name, which is widely used in his home country.
He has been an inspiration to millions around the world since emerging from 27 years imprisonment to become South Africa's first black president. He was awarded a Nobel peace prize and left office after one term in 1999.