It’s been nearly two decades since Princess Diana’s death, but it hasn’t gotten any easier for her sons Harry and William. In fact, Prince Harry recently admitted that he was not able to talk about his mother’s passing for quite some time.

According to a report from People magazine, the youngest of Diana’s two sons addressed attendees of a cookout he hosted at Kensington Palace. The event, which was attended by athletes and other important figures, was meant to benefit Heads Together — the mental health organization Princes Harry, 31, and William, as well as Princess Kate, support. During his speech, Prince Harry revealed something he has not often spoken about — he, too, struggled with mental health issues. He shared with those in the audience that he wishes he’d been more open about his loss after Princess Diana was killed in a car accident in August 1997.

“Everything can be OK, but I really regret not ever talking about it for the first 28 years of my life — I never talked about it,” he said. “Everyone can suffer from mental health, whether you’re a member of the royal family, whether you’re a soldier or a sports star.”

Prince Harry may not talk much about his mother’s passing, but he and Prince William, 34, have gone above and beyond to ensure that her legacy lives on. For his part, Prince Harry has been working hard to continue the efforts of his mother in reducing the threat of the AIDs epidemic. He recently submitted to HIV testing, which was broadcast on Facebook Live. In June Prince William and his wife jetted to India, where they retraced some of Princess Diana’s steps. The couple recreated the iconic photo of Princess Diana — published on Mirror U.K. — sitting in front of the Taj Mahal and visited Buhtan.

Prince William shared his own feelings about losing his mother in October 2015, during Child Bereavement UK. The Telegraph UK shared a video from the event, which showed the Duke of Cambridge discussing his mother’s death. He told attendees it was “the most painful experience,” adding that his mother dying at a young age has made him appreciate his children that much more.

Princess Diana died on August 31, 1997. At the time, she was driving in Paris with rumored boyfriend Dodi Al-Fayed. The pair were joined by security guard Henri Paul. Princess Diana and Al-Fayed’s car is said to have crashed into a concrete wall in a tunnel. It is believed they were trying to evade paparazzi at the time. Another car was also involved in the accident. The New York Daily News reported that that driver was also killed in the accident.