Serena Williams bared her soul and revealed a message she shared with rising tennis star Naomi Osaka in a recent essay published in Harper's Bazaar. 

Following her devastating U.S. Open loss last year, Williams has had time to reflect on her career and life. Her eye-opening essay, released Tuesday in Harper's Bazaar, also revealed her struggles with mental health.

She reportedly had trouble sleeping at night and needed to seek out a therapist to confide in. Even after opening up, Williams was not ready to return to the tennis court. 

“Days passed, and I still couldn’t find peace. I started seeing a therapist," she said. "I was searching for answers, and although I felt like I was making progress, I still wasn’t ready to pick up a racket.”

The events of the U.S. Open played over and over for her, but she always thought about how it all ended for Osaka. 

The then-20-year-old snagged her first major victory. However, the win was marred by controversy. Williams clashed with chair umpire Carlos Ramos and as Osaka was presented with her trophy, the Arthur Ashe Stadium was filled with boos. 

Williams sent an email to her apologizing for how the crowd responded. Additionally, the 37-year-old expressed regret for defending herself against Ramos sexist coaching call. 

“I thought I was doing the right thing in sticking up for myself … I would love the chance to live that moment over again.”

The 23-time Grand Slam winner knew how special Osaka's first win should be. Williams blamed herself for "robbing" her fellow tennis compatriot of the moment. 

"Not only was a game taken from me but a defining, triumphant moment was taken from another player, something she should remember as one of the happiest memories in her long and successful career," Williams wrote. "My heart broke."

The tennis great received a positive, uplifting email response from Osaka, instructing her to keep "trailblazing." 

"People can misunderstand anger for strength because they can't differentiate between the two," Osaka replied, according to Williams. "No one has stood up for themselves the way you have and you need to continue trailblazing."

The Compton native's personal essay went on to praise Osaka for her achievements thus far. She even touched on the general struggles of women expressing themselves in the workforce. 

"I would never, ever want the light to shine away from another female, specifically another Black female athlete," Williams wrote. "I can't wait for your future, and believe me I will always be watching as a big fan! I wish you only success today and in the future. Once again, I am so proud of you. All my love and your fan, Serena."