Chris Hyde/Getty Images(NEW YORK) — Serena Williams wrote a heartfelt essay for International Women's Day about the meaning of day to her and the lessons she wants to impart to her daughter.

The tennis star, who is an outspoken proponent of equality and empowering young women, described the special day as a "reinvigorated call to action," in her piece for Fortune.

She discussed some of the standards she feels are forced upon women in society.

"In our fast-paced world, expectations for women continue to rise, as do workplace demands and, unfortunately, double standards," she wrote.

"Navigating it all is especially tough for working moms, myself included —- I feel the pressure both on and off the court," she continued. "Even with all the resources I’m incredibly blessed to have, motherhood comes with so many unexpected challenges, especially when it’s time to go back to work."

She expanded on the balance she's trying to find between motherhood and her career, after giving birth to daughter, Alexis Olympia Ohanian Jr., in 2017.

"Now that I have Olympia, she is my absolute priority —- spending as much time as possible with her every day is so important to me," she wrote. "But I’m still training to win Grand Slams and sometimes I have to make hard choices about how I spend my time."

"I’ve cried over Olympia so many times that I’ve lost count," she continued. "I cried when I stopped breastfeeding. I sat with Olympia in my arms, I talked to her, we prayed about it, and I told her, 'Mommy has to do this.' I cried when I missed Olympia’s first steps because I was in training."

"I’m honest about my struggles as a working mom because I want other women out there to know they are not alone," she added. "We have to show ourselves and our female counterparts compassion and reality."

However, she realizes that she doesn't have to sacrifice her career choices in order to have a family.

"Since I was a little girl, I’ve dreamed of being the best tennis player in the world … but I also dreamed of having a family," she wrote. "The dream was not divided — it was to be successful in both arenas."

"I want to stay in this game long enough for Olympia to watch me, cheer me on, and be proud to say, 'That’s my Mom.' I want her and all women out there to know you can be whatever you want to be," she continued. "Dream big. The sky is the limit. Take risks."

She said that her dreams are "just beginning."

"I want Olympia to see and remember her mom winning a Grand Slam title," she wrote. "I want her to know that my work fulfills me, that I’m proud and passionate about what I do even if I’m not perfect at it, and that she should never give up on her dreams."

"I want her to see a world of possibilities at her feet and to believe in those first steps she took when I was training, every time she takes a leap toward her goals— however big the risk," she added.

In working to balance time with her daughter and being one of the most successful athletes in the world, she wrote that she's come to an important realization.

"I want to make it clear that perfection is an impossible goal and should never be a true pursuit in life. And this is something I’ve had to come to terms with myself," she shared.

Williams believes in the power of supporting other women and feels others should as well.

"While I think all women are superheroes, we are not superhuman and we need each other’s support," she wrote. "We need to give each other grace when we fall short—and when society sets unrealistic expectations or our workplaces have antiquated rules."

For the piece, she also asked SurveyMonkey, an online survey company for which she is a board member, to conduct surveys focusing on adversity women face in different aspects of their every day lives.

"One focuses on the experiences of working parents, while the other delves into those of all women in the workforce," she explained. "After reviewing the results, one thing is clear: many of us are facing strikingly similar challenges."

"Our data show that women are four times more likely to say they provide more childcare than their male partner—pulling a double shift at work and home," she explained.

"This contributes to the fact that nearly half of women say they have sacrificed career goals for their family. I know I did," she added. "More than half of moms feel guilty leaving their children to go to work and a third say their job makes it challenging to do the things they want and need to do for their family. Forget the cliché of ‘having it all,’ the reality is, women are trying to do it all."

Williams finished the piece with a call to action.

"On International Women’s Day, let’s promise to come together and support one another in honor of all the groundbreaking women who came before us—and those who are proudly following our lead.

"We must band together and fight for what’s fair," she added.

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