Zamaswazi Dlamini-Mandela says she remembers meeting her grandfather, Nelson Mandela, for the first time after he spent 27 years in prison. She had grown up hearing about him from her mother and grandmother, Winnie Madikizela-Mandela.

Dlamini-Mandela said her family, even from a young age, was acutely aware of his significance in the world and his fight for freedom. Understanding his courage, sacrifice and resilience made it somewhat more bearable for her to grow up without him, and even after his release, time with him was often bittersweet.

"It was really quite a joyful time but at the same time I think it was a bit sad because it made you remember what we lost as a family and what we now had to try and gain but essentially couldn't because all that time had gone by," Dlamini-Mandela told CBSN.

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She said she remembers never putting up a Christmas tree because her mother said there was still too much pain and suffering on Robben Island, where Mandela was held for 18 years, to celebrate. Still, there was hope he would be released, and he retained a sense of optimism in himself, his family and the anti-apartheid movement.

Now, in a new book, readers have a chance to see the activist and former South African president -- often hailed as the father of the nation -- in a powerful way. "The Prison Letters of Nelson Mandela" publishes more than 250 personal correspondences with family, friends and others. Dlamini-Mandela wrote the foreword to the book which was edited by Sahm Venter.

The letters give a deeper look into the everyday brutality he suffered, from his eyesight failing after manual labor in limestone quarries to the struggles Africans faced to attain basic needs as the lowest in the hierarchy of prison. The letters also show the painful struggle Mandela grappled with as he tried to retain his presence as a father.

In one he wrote that he wishes science "could invent miracles and make my daughter get her missing birthday cards and have the pleasure knowing that her pa loves her." Other letters detail his pain after the death of his eldest son, Thembi, and how he was not allowed to attend his funeral.

Still, Mandela's letters highlight the resiliency, steadfast vision and empathy the anti-apartheid revolutionary was known for. In one letter, he reflects on academic writings on positivity, saying "it is not so much the disability one suffers from that matters but one's attitude to it. The man who says: I will conquer this illness and live a happy life, is already halfway through to victory."

His message of hope even in the most desolate of times is emblematic of both his personal and public persona. Mandela was celebrated around the world this week for what would have been his 100th birthday. After he was imprisoned from 1962 to 1990, he served as the first democratically elected president of South Africa and received the Nobel Peace prize.

"I think my grandfather was a very special human being and I think, although, he didn't like to be treated that he was special but I don't know how many people or any of us could have done what he did and in the manner in which he did it: dignified, respectful, resolute, calm," said Dlamini-Mandela.

"In modern day I feel it's good that we can hear his voice because this is his own words and you can hear his voice when you're reading it and it's a beautiful thing. I think we need it in a world today when we just need to be to reminded that so much was given and so much was lost and hopefully, I pray, we build from that."