The mercurial Australian has long been open about his struggles with mental health and said he is proud to have bounced back after being in some "scary places" in recent years.
"I felt like when I was really struggling mentally, I was very selfish," he told reporters.
"I felt like, I feel bad, I don't want to play. Then I looked at the people closest to me and how much I was letting them down, and I didn't want to do that anymore."
The immensely gifted 27-year-old said he decided to put his focus into getting into great physical shape, which was on full display as he battled past Medvedev on a hot and humid night at Arthur Ashe Stadium to reach the tournament's quarter-finals for the first time.
The Wimbledon finalist has won 26 of his last 31 matches and said all of that success has given him the motivation to train even harder.
"I feel like I'm making people proud now," he said.
"There's not as many negative things being said about me. I just wanted to turn the narrative around... I just was feeling so depressed all the time, feeling sorry for myself. I just wanted to change that."
Despite the heartfelt nature of the press conference, Kyrgios could not help but toy with reporters, suggesting he may simply walk away from the sport if he captures his maiden Grand Slam title at the last major of the year.
"We've got to try and just tough it out and keep pushing each other, keep being positive," he said.
"We do realize it's next week we're going home. Three more matches potentially, then we never have to play tennis again," he said with a smile.
