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Gymnast Simone Biles shocked the world on Tuesday when she made the decision to withdraw from the Olympic gymnastics team final competition. Biles cited her mental health as the reason for withdrawing from the competition and didn't want to put her teammates at a disadvantage. She followed up that move by also pulling out of the individual all-around less than a day later.

When Michael Phelps -- who as his height was an iconic American Olympic athlete in the same way Biles is -- heard about her decision, he was extremely supportive.

"It broke my heart. But also, if you look at it, mental health over the last 18 months, is something that people are talking about," Phelps told NBC's Mike Tirico.

Phelps is one of the very few who can relate to what Biles is going through. During his swimming career, Phelps dealt with anxiety, depression, and even suicidal thoughts. And that's while he was the face of the United States during every Summer Olympics he competed in.

As a result of his personal experiences, Phelps has become a big advocate for mental health. The former Olympian even has the Michael Phelps Foundation, which preaches to kids the importance of being active and healthy.

"The Olympics is overwhelming. There are a lot of emotions that go into it," Phelps added about Biles' situation. "I can talk about this for an hour. The easiest way for me to say it is I think athletes, and Olympic athletes in general, we need someone who we can trust. Somebody who can let us be ourselves, listen and allow us to become vulnerable. Somebody who is not gonna come try to fix us.

"... We're human beings, nobody is perfect. It's ok to not be ok. It's ok to go through ups and downs and emotional roller coasters ... I felt like I was carrying, as Simone (Biles) said, the weight of the world on my shoulders. It's a tough situation." 

Biles had one attempt in the vault portion of Tuesday's team final competition before bowing out. The United States rallied behind their teammate and earned a silver medal behind the Russian Olympic Committee, who won gold.

Phelps understands the immense pressure that Biles was under, considering that she is often labeled as the greatest gymnast of all-time.

"I hope this is an eye-opening experience, I really do," Phelps said. "I hope this is an opportunity for us to jump on board and to even blow this mental health thing even more wide open. It is so much bigger than we could even ever imagine. This is something that's gonna take a lot of time, a lot of hard work and people who are willing to help."