Serena Williams has lifted the lid on her immediate thoughts following her career-ending loss to Australian star Ajla Tomljanovic at last year's US Open.

Williams returned to Flushing Meadows searching for a fairytale end to her incredible tennis career, but Tomljanovic spoiled those plans with a 7-5, 6-7, 6-1 third round win in New York. 

The 41-year-old left the court in tears and has now recalled her emotions the morning after that poignant farewell in September. 

'I was actually not very happy at all, just because of the result,' she told CBS.

'I was there to keep going and to keep winning, and it was more or less like, I can't believe I let that match go more than anything...

'Obviously it was a great moment and a great memory and I don't feel like I've left anything, but I just felt like what I could have done better that day.'

Despite dedicating two decades of her life to the sport, Williams has no interest in making a return to the court and is enjoying life post-tennis. 

'I feel relief when I look at the court,' Williams said.

'I feel like I am so happy I don't have to train for two hours today...

'I've literally given my whole life to tennis. It's time for me to give my life to something else.'

Williams is married to Reddit founder Alexis Ohanian. The pair have a five-year-old daughter, Alexis Olympia, who is keen on becoming a big sister. 

'The other day she's like, "Everyone has a brother or a sister but me." And I'm like, "Olympia, I'm working on it. Mommy worked a little too long in tennis, so it's takin' a little longer than expected,"' Williams recalled.