Usually at this time of year, Serena Williams would be preparing for January's Australian Open and she appears be finding it difficult to fill the extra time on her hands.

After an emotional goodbye to tennis at the US Open in August and September, the 41-year-old has been adjusting to life away from the court. 

But with the next major on the horizon on the tennis calendar and extra downtime during the holidays, she took to Twitter to admit that retired life isn't easy.

'I’m currently allowing myself to be tired,' she wrote. 'Allowing myself To relax. Allowing myself to just be. It’s harder than I ever imagined. I’ve never allowed myself to do any of that before…'

Earlier on Wednesday, she had posted a picture with her daughter Olympia and husband Alexis, saying how they had thrown their five-year-old a surprise party.

'Sometimes we surprise Olympia with parties,' Williams wrote on Instagram. 'We don't need a reason or a special occasion we make everyday as special and memorable as we can. Also her mama fast.....'

Williams announced her retirement with an article in Vogue back in August and said it was in part because she wanted another child.

'I have never liked the word retirement. It doesn’t feel like a modern word to me,' she said. 'I’m here to tell you that I’m evolving away from tennis, toward other things that are important to me.

'I never wanted to have to choose between tennis and a family. I don’t think it’s fair. If I were a guy, I wouldn’t be writing this because I’d be out there playing and winning while my wife was doing the physical labor of expanding our family. But I’m turning 41 this month, and something’s got to give.' 

Despite stepping away after the US Open, Williams has said that she could one day return to the court but her latest tweet about allowing herself to relax also appears to end any suggestion she could play in the Australian Open next month.

Speaking at a tech event in San Francisco in October, 23-time Major winner Williams said: 'I am not retired.

'The chances (of me returning) are very high. You can come to my house and see I have a court.

'I still haven’t really thought about it. But I did go on the court the other day and realized for the first time in my life that I’m not playing for a competition and that felt very weird.. 

'It was like the first day of the rest of my life, and so far, I am enjoying it. But I’m still trying to find that balance.'