World number one Serena Williams says a fierce competitive streak keeps her motivated despite a decade of dominance, warning competitors Sunday that she is determined to extend her sparkling 2013 form.
Speaking in Brisbane where she will be defending the title she won earlier this year, Williams said she had kept her off-season to a minimum to avoid any impact on her momentum.
Williams had only four losses in a stellar 2013, a year that included her 16th and 17th Grand Slams at Roland Garros and the US Open.
In a warning to her rivals, she said she was determined to take her 2013 form into the new season.
"I took a couple of weeks off, but I was already like kind of itching to get back on the court," she said of her short off-season.
"I didn't want to lose any rhythm or anything -- didn't want to lose momentum is the word I was looking for. I definitely wanted to move forward with that."
Despite a decade of dominating the world circuit, a smiling Williams said a love of the contest kept her going.
"I don't know why. Why am I training so hard in Florida with my dad? Why am I, like, doing this so many years later?" she said, when asked what sustained her.
"I can't stop. I love it. I love being out here. I love competing.
"It gives me something to do, and I just love the competition. So for me, it's just about motivating myself and trying to reach new goals."
Williams said playing in the heat and humidity of Brisbane was the ideal preparation for January's Australian Open, the season's first major.
On a day when the temperature on centre court climbed above 40 degrees Celsius (104 Fahrenheit), Williams said thoughts of wining an 18th Grand Slam made her choose Brisbane to start the 2014 season.
"I definitely thought about going somewhere else, but it just didn't feel right," she said.
"I think it'll give me a really good preparation.
"It's a great tournament to play -- obviously the same surface (as Melbourne). Hopefully it'll stay hot like this, because I think the heat is good preparation for the main event."