Why Kate Middleton Is Retreating from the Spotlight After Wimbledon: ‘She Will Be Back’ (Exclusive)

Kate Middleton’s appearance at Wimbledon was likely her last public outing before a quiet summer.

The Princess of Wales, 42, stepped out at the tennis tournament with her daughter, Princess Charlotte, and sister, Pippa Middleton, for the men’s singles final in just her second public event of the year amid her cancer treatment.

Robert Jobson, author of the new book Catherine, the Princess of Wales: A Biography of the Future Queen, out Aug. 6, tells PEOPLE exclusively in this week’s issue, “Before, she used to live her life by the calendar, and now she is living her life, and the calendar comes in after.”

“She will be back, but when you have had an experience like this, it changes your perspective and the order of things,” he says.

Princess Kate would usually attend Wimbledon finals with her husband, Prince William, but he took their oldest son, Prince George, to watch England’s soccer team play in the final of the Euros against Spain in Berlin. The family was soon reunited, and they are now looking ahead to a summer of seclusion, privacy and continued healing for her.

They’re likely to spend much of it at their country home of Anmer Hall, close to the beaches of north Norfolk, where the family enjoys outings and boating. A late-summer stay at Balmoral Castle hosted by King Charles, 75, who is facing his own cancer treatment, will be factored in too.

“She won’t have to be on center stage,” a palace insider tells PEOPLE. “Being with her family and just being herself will give her energy. There will be plenty of time to focus on her recovery.”

Despite being front and center in the Royal Box at Wimbledon for about two hours and 40 minutes, Princess Kate appeared to have gained some comfort from the warm welcome and being out and about.

“This will have given her sustenance. She has gone through something awful and stressful, and it is crucial to have little wins to look forward to or to give you the courage and energy to go forward,” the palace insider says. “And this was it.”