Prince William talks about the shock of losing his mother and how he’s never truly recovered

VENICE, ITALY - MAY 5: (FILE PHOTO) (L-R) Diana the Princess of Wales holds her son Harry, whilst looking at Prince William held by his father Prince Charles on May 5, 1985 in Venice, Italy. Prince William will celebrate his 21st birthday on June 21, 2003. (Photo by Georges de Keerle/Getty Images)

It’s almost been 20 years since Princess Diana tragically passed away, but Prince William still isn’t completely over his mother’s death.

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The shock is the biggest thing,” he reportedly says in the new BBC documentary “Mind Over Marathon,” which will air in the United Kingdom on Thursday. “I still feel, 20 years later about my mother, I still have shock within me. People say shock can’t last that long, but it does. You never get over it. It’s such an unbelievably big moment in your life that it never leaves you, you just learn to deal with it.”

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“Mind Over Marathon” follows stories of ten London Marathon runners who struggle with mental health issues. In it, Prince William opens up about his own loss and how he learned to deal with his grief.

“You try and understand your emotions a lot more than probably someone who’s just lived life without issues, and that’s quite critical,” he continues. “It’s explaining to them what those emotions mean, why they feel like they do. Once you start rationalizing a little bit and you understand, ‘Okay, so I’m a little angry or a little down or a little upset about something,’ then you can kind of relativize it and sort of deal with it.”

On Tuesday, the royal spoke further about his own personal struggles and his advocacy for mental health awareness through his Heads Together Campaign alongside brother Prince Harry and wife Duchess Kate.

“I have my own reasons for being involved in mental health: What happened to me and my mother when I was younger,” he said. “It all comes back down to mental health.”

RELATED: Prince Harry reveals he “buried” his emotions after Princess Diana died and shared how he got his life back on track

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