Serena admits she is a "perfectionist". Picture: Instagram

Serena Williams admits it is a juggling act to run her eponymous sportswear brand, commit to her intense tennis training and raise her daughter.

Serena Williams "doesn't know" how she juggles running her fashion business with her tennis career and her responsibilities as a mother.

The 37-year-old sports superstar launched her own eponymous clothing line in May and she is very hands-on with the business even though she is still playing tennis professionally and she admits she has to be on top of her time management as she is also raising her 14-month-old daughter Alexis Jr. with her husband Alexis Ohanian. 

In an interview with Teen Vogue, she said: "Honestly, I don't know. I go to bed every night thinking, 'How did I get through this day?' I'm sure a lot of people out there can relate, right? It's like, this day is over, it's 10 o'clock, I got through it. How did that happen? That's kind of how I am. 

"Now I'm training on top of running this fashion company, on top of being a full-time mom. I'm super hands-on as a mom. I just take it as it is and realise that everyone goes through the same thing."

Serena admits she is a "perfectionist" but she has learned that not every day go can the way she wants in her work and that has allowed her to get a better handle on her working days.

She said: "I think it's really important to realise that no day is going to be perfect. For me, that's really hard because I strive for perfection, and I feel like everything I do has to be great and has to be perfect, because I am a true perfectionist. 

"But that's impossible. That's not reasonable. Then I realise that, okay, I had a rough day today, let's do something to make it better tomorrow. I think it's important to expect to have some really rough times when you're going through something, but always know that you can overcome it."

As well as her own label, Serena - who has become synonymous with style in the world of sports - previously teamed up with one of the fasting rising names in fashion, Off-White founder Virgil Abloh, for a limited edition tennis range for sportswear giant Nike.