Kate Middleton ‘Is Looking After Herself’ as She Marks Birthday (Exclusive)

Kate Middleton is putting herself first as she rings in her birthday four months after announcing that she completed chemotherapy treatment for an undisclosed form of cancer.

The Princess of Wales turned 43 on Jan. 9, celebrating her first birthday after a difficult year. In March 2024, Princess Kate announced that she was undergoing treatment for cancer and shared in September that she completed chemo. In a rare revelation at her Together at Christmas carol service in December, Princess Kate said, “I didn’t know this year was going to be the year that I’ve just had.”

Looking ahead, a family friend exclusively tells PEOPLE that the Princess of Wales, described as “a real running, skipping and jumping” type of sporty person, is wisely prioritizing her health now.  

“She is looking after herself and is wise to do so. She will know when she wakes up if she is well enough or not [to do something],” the family friend says.

Robert Hardman, author of The Making of a King: Charles III and the Modern Monarchy, points out that the princess may still be on the mend.

“We are being encouraged not to look at this as a chapter that’s over and then it’s back to normal, because cancer doesn’t work like that,” Hardman tells PEOPLE. “The details remain private but there’s no getting over the reality that it’s an unpredictable disease.”

“The clue is in her phrase ‘one day at a time’ — that’s how she’s going to approach it,” says Hardman, referring to a line in her Sept. 9 announcement about completing chemo. The Princess of Wales said in that video message, “Doing what I can to stay cancer free is now my focus. Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes.”

Adds a source, “She has been allowed to get back in her own way. She has been able to pace it and do it her way, and that’s great.”

The Princess of Wales was most recently seen on Christmas Day, where she stepped out in sync with Prince William and their kids Prince George, 11, Princess Charlotte, 9, and Prince Louis, 6, for church at St. Mary Magdalene on the Sandringham estate.

The royal was in her element as she chatted with well-wishers, and many of her meaningful conversations with those gathered were about cancer. King Charles was also diagnosed with an undisclosed form of cancer last February, and palace sources say his treatment is “moving in a positive direction” as it continues in 2025.  

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“Family has seen [Kate] through thick and thin this year … There is a sense of optimism going forward,” an insider says.

Princess Kate is spending her birthday at home with Prince William and their children, who recently returned to the classroom at the Lambrook School after a holiday break.