Queen Elizabeth II is 95 years old and still going strong. Despite the fact that she has been on the throne for 70 years, she is still considered to be one of the world's most positive people. 

However, there appears to be a trick to how she accomplishes this. 

In celebration of the Queen's Diamond Jubilee, royal author Robert Hardman wrote "Queen of Our Times: The Life of Elizabeth II," a biography of the monarch. 

He appeared on BBC Breakfast per Express, where he informed viewers that he had had the opportunity to speak with international leaders and royal authorities about the Queen of the United Kingdom. 

Despite the scandals and drama that have surrounded the British royal family, the author also revealed the monarch's secret. 

After interacting with a variety of people and researching research on Queen Elizabeth II, I came to the conclusion that "she possesses an underlying steely confidence and is very optimistic, even in the most difficult of circumstances." 

"She is an optimist," he remarked, adding that she "rarely appears depressed." 

According to the author, her "endurance" was fueled by three factors: "good health, strong faith, and Prince Philip," to name a few. 

Although the Duke of Edinburgh passed away last year, the Queen demonstrated that she was able to carry on with her responsibilities even in the face of her loss. 

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Queen Elizabeth II's Friendship With Nelson Mandela 

Robert was interviewing a number of Prime Ministers for the book at the time and many individuals shared their thoughts about Queen Elizabeth II's outstanding relationship with Nelson Mandela. 

The expert stated that they became friends immediately after meeting and that their friendship continued throughout his term in office and into the future. 

They initially met in 1991 when attending a reception for Commonwealth leaders in Zimbabwe. 

Several royal protocols are also said to have been violated by the late South African anti-apartheid leader Nelson Mandela. He was the only world leader who was able to address the Queen simply as "Elizabeth," which was a rare occurrence. 

According to the book, Nelson once greeted her in London, long after he had left office as president, by commenting, "Oh Elizabeth, you have lost weight." 

"None of her friends would have dared to say that," Robert remarked, "but she thought it was incredible, and Nelson could get away with whatever he wanted." 

When Nelson Mandela died in 2013, Queen Elizabeth II was unable to attend his funeral. She issued a statement in which she said she was "deeply saddened" by what had happened and that she had been prevented from attending owing to security concerns.

READ MORE: Queen Elizabeth II Needs to THIS to Be Able to Attend Prince Philip Memorial