Prince Harry told the U.K. Telegraph's Bryon Gordon that he "shut down all [his] emotions” for almost two decades due to the grief over the death of his mother, Diana, the late Princess of Wales.
He also described feeling completely overwhelmed having to live his life so publicly.
"I have probably been very close to a complete breakdown on numerous occasions when all sorts of grief and sort of lies and misconceptions and everything are coming to you from every angle,” Harry told Gordon.
He credits his brother, Prince William, with encouraging him to seek out mental health support to help him deal with his anger and his pain.
"For me personally, my brother, you know, bless him, he was a huge support to me. He kept saying, 'This is not right, this is not normal, you need to talk to [someone] about stuff, it’s OK.'"
William and Harry rarely speak so candidly about their mother but have recently opened up in order to help others struggling with mental illness.
“My way of dealing with it was sticking my head in the sand, refusing to ever think about my mum, because why would that help? It’s only going to make you sad, it’s not going to bring her back," Harry said. “So I was a typical 20-, 25-, 28-year-old running around going ‘life is great’, or ‘life is fine’ and that was exactly it."
He also said he took up boxing to help channel his aggression. He described a period of two years that were total chaos while he reached out for help.
"And then [I] started to have a few conversations and actually all of a sudden, all of this grief that I have never processed started to come to the forefront and I was like, there is actually a lot of stuff here that I need to deal with,” Harry said.
Harry said in the podcast that the counseling and support he received has changed his life
"Because of the process I have been through over the past two-and-a-half years, I’ve now been able to take my work seriously, been able to take my private life seriously as well, and been able to put blood, sweat and tears into the things that really make a difference and things that I think will make a difference to everybody else," Harry said.
On Sunday, the fifth in line also released a message of support that was broadcast over the Fenway Park Jumbotron for Iraq War heroes Ivan Castro and Karl Hinnett.
"Ivan and Karl are two American and British veterans wounded in battle that I've had the privilege of calling my friends," Harry told a cheering crowd at Fenway. "Tomorrow they will run the Boston Marathon for Heads Together, the campaign that Catherine, William, and I are leading to change the conversation on mental health."
Hinnett and Castro were at Fenway to throw out the first pitch at a Red Sox game ahead of the marathon Monday.
Castro lost his sight when a mortar landed a few feet from him causing injuries many thought he would never survive. The officer fought back and still serves in the Special Forces, inspiring active and injured service members in their own recovery. He accompanied Harry on the "Walking with the Wounded" trek to the South Pole and has been a huge supporter of Harry's Invictus Games. Hinnett, a British soldier, suffered burns over one-third of his body when his tank was set ablaze in Basra, Iraq. The soldier underwent more than fifty operations and has competed marathons of five continents including the North and South Poles.
A week later, the two Iraq heroes will attempt the London Marathon, running for Heads Together there.
"They're taking on the incredible challenge for one reason, to help us end the fear that stops people talking about mental health," Harry said.