Three months ago, Serena Williams was at her lowest after going out in the first round of the French Open, her earliest exit at a grand slam.
She was miserable after that defeat, but also at her most dangerous. On Sunday, the 30-year-old American capped off a 'golden summer' by winning a fourth US Open crown for her 15th slam singles title.
Her victory in the last grand slam of the season came after she won Wimbledon and singles and doubles gold medals at the 2012 London Games.
"Losses really motivate me," Williams said after a champagne toast at her news conference following her 6-2 2-6 7-5 victory over world number one Victoria Azarenka in a thrilling US Open women's final.
"I was miserable after that loss in Paris. I have never been so miserable after a loss," she said of her defeat to 111th-ranked Virginie Razzano of France.
"I don't know if that helped me, the loss in Paris. I like to believe it did, because I just wanted to do more. I wanted to do more and more and more." After beating Australian Open champion Azarenka on Sunday, Williams collapsed on her back and covered her face in shock.
"This is the most best feeling I think in tennis," she said. Williams has had to overcome more than defeats. She battled a slew of injuries over the last few years, including a severe foot injury and life-threatening blood clots in her lungs, and also had behaviour issues that plagued her at the US Open.
The power-hitting Williams has managed to come through it all in brilliant fashion, showing she still has the skill, will and enthusiasm to rule the women's game. "I was in the hospital last year," said Williams, who checked herself in after having trouble breathing and was found to have the blood clots. "So it means a lot. To win Wimbledon is always so special, but coming to your home country and winning this one is just awesome. To win two in a year, it's great."
Williams said she tried to think on the positive side, but has perspective about the challenges that must be faced. "I don't think about the downs too much. I hope I never think about them as my life continues," she said.
"But I really think a champion is defined not by their wins but by how they can recover when they fall. "I have fallen several times. Each time I just get up and I dust myself off. So I feel really awesome that I have been able to do that. "You see great people like Muhammad Ali, for instance, who is a complete person I have always looked up to in sports. He went to jail for so long and he came back as a champion again.
"So I just really think that really defines a champion." Williams's previous two trips to the US Open ended with matches in which she badly lost control of her temper. She threatened an official on court for calling a foot fault on her in the 2009 semi-final against Kim Clijsters, and insulted the chair umpire when she was punished for screaming during a point against Sam Stosur in last year's final. There was a moment in Sunday's final against Azarenka that tested Williams's self-control after she was assessed a foot fault in the second set and glared at the chair umpire.
"This is the first year in a long time I haven't lost my cool," she said, drawing a laugh from reporters. "I think everyone thought about last year. (But) I was just thinking, OK, which foot was it? So I would know not to do that again."
Her extraordinary 2012 summer of success is extra special considering she began her run as a grand slam champion 13 years ago when she won the US Open crown as a 17-year-old. Asked to compare herself to the teenager who the 1999 title, Williams said:
"We both have so much to look forward to. I feel like even though I'm 30, I feel so young and I've never felt as fit and more excited and more hungry.
"Even with this win, (I'm) so excited still to play the next grand slam and see what I can do. Just to do more, I love that feeling. "I will think about my legacy when I'm done."