Mandela's anti-apartheid activism resulted in his being imprisoned for 27 years by the white government. He was released in 1991 and since then has championed reconciliation between South Africa's blacks and whites.
They may be free, but black South Africans still face numerous obstacles, including poverty, crime and an HIV epidemic.
Mandela, 91, has called on his nation to heal the wounds of its past and build a better future. Even in the face of opposition, he has always advised against revenge actions, Machel said.
She said she believed her husband would be remembered as the "visionary leader" who, with humility, was able to unify a fractured nation.
Mandela, who is viewed as the father of the new South Africa, is welcomed with warmth and respect wherever he goes, and he continues to be in great demand.
Supporters and admirers constantly request his presence, but some days, he just can't comply. At his age, the constant scheduling is difficult.
"You know, Madiba is healthy, he's really healthy. He is old, I mean, the body is tired. But his spirit is strong as ever," his wife said.
Machel, a social activist, is a former education minister of Mozambique and was married to that country's president.
She said the World Cup has profound implications for South Africa's future. South Africa should build on the honor of hosting the world-class competition and use it to devise a concrete plan for improving the education of its youth, she said.
"What is it going to mean when the game is over, for children for instance?" she said. "So this idea of creating an education, legacy trust which would help children who are out of school to have access to education, it can be done."