Princess Diana overcame her mental health disorder by doing physical exercise three times daily.

Jenni Rivett, the celebrity trainer that worked with the late Princess of Wales, said that the mom of two learned how to use her workouts as part of her healing process. While she was still alive, Princess Diana battled bulimia, and she also struggled with her marriage to Prince Charles.

But despite her mental disorder and other issues, Rivett said that Princess Diana never wanted her illness to bring her down.

“Actually she had an incredible sense of humor. The way that was brought up was with a joke. She was just trying to make light of it,” Rivett told Express.

Within a short time of working with each other, the celebrity trainer said that Princess Diana developed a sense of discipline. She also attended her training sessions regularly and was very dedicated.

Princess Diana previously admitted to suffering from bulimia nervosa during an interview. She said that everyone from her family knew about her eating disorder, and everyone blamed her bulimia for the fallout of her marriage to Prince Charles.

Prince William and Prince Harry’s mom also said that the eating disorder was her discreet way of harming herself. But according to Rivett, Princess Diana also wanted to free herself from her disorder that’s why she worked out regularly.

“When you train with someone and they start to feel the strength going through their muscles it is so empowering and just so much to make you not want to go that direction again… The challenge was that she was the Princess of Wales. There was a lot of stuff in her life,” Rivett said.

Princess Diana passed away on Aug. 31, 1997, following a fatal car crash in Paris. At that time, she and Prince Charles have already ended their marriage for a year. Prior to her death, Princess Diana learned that Prince Charles was having an affair with Camilla Parker Bowles, and this also contributed to the failure of her marriage.