Ahead of the June 15 Trooping the Colour in London — her first official appearance in six months — Princess Kate Middleton shared an update on her cancer treatments, which she said will continue for a few months.

“As anyone going through chemotherapy will know, there are good days and bad days,” Kate, 42, wrote on social media. “On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well.”

If Kate’s glowing smile at King Charles III‘s official birthday celebration is any indication, her public return was definitely a good day! “Kate was nervous making her reappearance,” a source exclusively tells Life & Style. “She worried she would look tired or too thin at the parade, but she looked amazing. The supportive response Kate got boosted her confidence, and it was apparent.”

Kate wanted to show the world she hadn’t given up — and she did so with the style and grace that have made her so beloved. “Prince William was very proud of her,” notes the insider, “and so were the rest of the royal family.”

Kate Middleton Is Opening Up

That doesn’t mean the outing wasn’t hard on Kate, who’s been largely taking things easy at Anmer Hall in Norfolk with William, 42, and their kids: Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6.

“Kate was exhausted afterward,” says the insider. “It was a long day, and it took a lot out of her.” Though Kate has yet to divulge the type of cancer she’s fighting, she is making an effort to be honest about her ordeal. “That’s why she wrote that June post,” the insider adds. “She absolutely has bad days, and that’s something she wouldn’t have shared in the past.”

Kate Middleton Was ‘Exhausted’ After Her Public Appearance
HENRY NICHOLLS/AFP via Getty Images

But she’s now attempting to turn her negative into a positive. “Kate’s not the only person battling cancer, and she realizes that being truthful about her struggle will help others,” explains the insider. Along those lines, Kate didn’t commit to attending more events, saying she’s “learning how to be patient.”

While the princess revealed that she hopes to attend “a few engagements” this summer, she knows she’s “not out of the woods yet.” Whenever she does reemerge, the public will more than welcome Kate.

“Her display of strength proves she’ll make a worthy queen one day,” says the insider. “She’s a fighter, for herself, her family and her country.”