Nothing drives Serena Williams the way disappointment does.
"It's the biggest factor for me. If I lose, all hell breaks loose. I go home, I practise harder, I do more," she said. "I don't like to lose. ... I hate losing more than I love winning. It could be a game of cards - I don't like it. I really don't like it."
The way Williams has been playing, there's been very little not to like. When Wimbledon starts tomorrow, she will be an overwhelming favourite to win her sixth title at the All England Club and second in a row.
Williams enters the grass-court grand slam tournament with a 43-2 record in 2013 and on a 31-match winning streak, the longest on the women's tour in a single season in 13 years.
"It happens in sports: You're going to lose. I learned that you're not going to win all of them. And there have been a few matches that I wasn't disappointed in," said Williams, who at 31 is the oldest player to be ranked No 1 in WTA history. "But there were some that I was disappointed in," she added, "and it's actually helped me to get better."
A little more than a year ago, Williams arrived at the French Open unbeaten for the season on red clay and anticipating a charge at the title. Instead, she lost in the first round, the only opening-match exit from a major tournament in her career.
"It really was a shock for her. She really worked on rebuilding herself to become perhaps stronger than ever," said Patrick Mouratoglou, the French coach who began collaborating with Williams shortly after that defeat.
"The more you eat, the hungrier you get," Mouratoglou said. "When you win, when you achieve the exceptional, you don't want it to stop."
Since that dark day at Roland Garros, Williams is 74-3, including trophies at three of the past four slams and the WTA Championships, plus gold at the London Olympics.
That run of nearly uninterrupted success began 12 months ago at Wimbledon, and most recently resulted in her first French Open championship in 11 years. Given the way Williams' best-in-the-game serve and generally dangerous strokes only get better on the slick grass, it's difficult to pick against her during the upcoming fortnight.
She is just two grand slam titles behind the 18 won by Chris Evert and Martina Navratilova and four back from the 22 racked up by Steffi Graf, but believes her best years may still be ahead of her.
"I'm really relaxed. I really enjoy every moment that I'm out there. I always said that I felt like I have never played my best tennis," said Williams, who became the oldest Roland Garros winner in the Open era when she beat Maria Sharapova in the final this month.
"I feel like I can always do better and play better and I have always wanted to reach that level. Maybe I'm just trying to get there. I really believe age is a number at this point, because I have never felt so fit. I feel great. I look great."
Her serve, which she can consistently hit at more than 190km/h, is clearly unrivalled and she leads the tour this season in aces, service games won, break points saved and first serve points won. Her return is terrific, too, and Williams leads the way in first serve return points won, while ranking second in return games won.
"I don't see a weakness," three-time Wimbledon champion John McEnroe said. "She's playing the best tennis of her career. She's not only in the best place I've ever seen, she's the best player that's ever lived. I said that a while ago, but she's cementing it in everyone's mind. She's just a level above anyone. There's no doubt about it."
Ask Evert how a player should try to beat Williams on a grass court, and the question is met with a lengthy pause. Then comes Evert's scouting report, which begins with the ominous-sounding warning that unless an opponent serves very, very well, Williams is liable to win 6-0, 6-0.
Evert goes on to suggest standing close to the service line for returns and chipping the ball back, perhaps luring Williams forward. "She beats everybody from the baseline, but nobody's really tried forcing her to come in. As good a volleyer as she is because of doubles, she's still not as comfortable at the net as she is on the baseline. I would take off some of the pace," said Evert, who will join McEnroe as an ESPN analyst during Wimbledon.
"You really can't hit with her from the baseline," Evert continued. "You've got to either hit short angles, drop shots, chip - do something to throw her timing off. Once she gets in a rhythm, she's deadly. But you've got to have a big serve. You have to be able to hold your serve. You can't be just slugging balls with her. That's been proven a thousand, million times: It doesn't work."
Little works these days against Williams, who might be as formidable now as she was at the height of her powers, more than a decade ago, when she won four consecutive major titles for a self-styled "Serena Slam" in 2002-03.
Williams beat her older sister in each of the finals during that stretch; Venus pulled out of this year's Wimbledon because of a lower back injury last Tuesday, a day after her 33rd birthday.
It's the latest setback for the elder Williams, who has lost in the first round at two of the past four major tournaments. As Serena's dominance increases, Venus could be nearing the end of her playing days, which have become more complicated because of the energy-sapping autoimmune disease she revealed in 2011.
"What's happened with her sister, the difficulties she's had as she's gotten into the later stages of her career, in a way helped Serena, because it made her realise she wanted to take advantage of these last couple of years," McEnroe said. "She realised, and maybe appreciated a little bit more, the talent that she has."
Williams' confidence is bad news for Russian world No 3 Sharapova, who is seeking a second Wimbledon title, nine years after her first. Sharapova's defeat in Paris was her 14th in 16 meetings with the American, with her last win coming back in 2004.
Australian Open champion Victoria Azarenka is seeded second and the Belarusian will be looking to go further than the semi-finals she reached in the last two years at Wimbledon.
Poland's Agnieszka Radwanska, who took a set off Williams in last year's final, is seeded four but her grass-court campaign got off to a terrible start on Tuesday when she was dumped out of the Eastbourne warm-up tournament in the first round by US qualifier Jamie Hampton.
"I've loved Wimbledon since I was young and won the junior tournament there in 2005," Radwanska said. "Wimbledon is the focal point of the summer for most of us pros. My sister and I rent a lovely house just across from the practice courts and we walk everywhere - to the courts, the shops and the restaurants. It's a luxury we don't have at most tournaments. And the interaction with fans there is great."
Sixth seed Li Na leads the Asian challenge. Li's Wimbledon best was reaching the 2006 and 2010 quarter-finals, though the 2011 French Open winner tumbled in the second round on her past two All England Club outings. Li said it was tough to switch from the Paris clay. "You play grass, you have to use your legs a lot so at least I have strong legs," she said.
Additional reporting by Agence France-Presse