Serena Williams poses with the U.S. Open trophy in New York’s Central Park. It’s the 15th major title of her career and second in 2012. (Mike Stobe/GETTY IMAGES)

After fighting through mid-match sluggishness and storming back from a 3-5, third-set deficit to win her fourth U.S. Open championship, Serena Williams went out for a night of karaoke in New York.

She performed for nearly three hours, compensating for an admittedly poor voice with fabulous dramatic skills, and didn’t get to bed until nearly 3 a.m.

Her signature song? Gloria Gaynor’s disco classic, “I Will Survive.”

“I thought it was a great story for me to sing last night,” Williams told a small group of reporters Monday, following a morning of media appearances. “I really, really felt those words.”

Indeed, the anthem of resilience fit Williams as perfectly as her cream Michael Kors sheath and the Christian Louboutin stilettos that added at least 5 inches to her 5-foot-9 height, a stunning ensemble for the Central Park photo shoot and CBS interview she had just completed.

Williams won the 15th major of her career, and her second of 2012, roughly 18 months after being hospitalized with a pulmonary embolism that relegated her tennis career to an afterthought.

“My goal wasn’t even to play anymore; it was just to be healthy,” Williams recalled of her hospitalization. ‘I thought, ‘Wow, I’ve had a great career. I just want to be healthy and make it out of here.’ ”

That she has returned to dominate women’s tennis is remarkable on several levels. The life-threatening health crisis is surely among them. Also notable: The fact that she turns 31 on Sept. 26 and, on Saturday, set a record for years between major titles by winning this U.S. Open 13 years after she won her first, the 1999 U.S. Open at age 17.

Contrary to prevailing locker-room sentiment, Williams’s resurgence has not been a matter of simply suiting up and flipping a switch.

“I’ve run into so many people on tour who say, ‘Oh, you just show up, and you win matches!’ ” Williams said. “I just smile and let them believe that. But the fact of the matter is, I probably work harder than anyone else on the [women’s professional] tour. Unless, I wouldn’t be here talking to you guys.”

Asked to elaborate, Williams said that a typical day between tournaments starts with a two- to three-hour practice. Then she works out at the gym for two hours. After that, she dances for three hours, then stretches for an hour.

“And then,” she said with a laugh, “die!”

Dinner at home typically caps the day off. And she repeats the routine day after day.

“I don’t have a life, especially lately,” she added. “I’m okay with that; I’m fine.”

Williams confided that her last serious relationship ended earlier this year, in January or February.

“The guy’s over me,” she said. “That’s fine; I’m over him, too.”

Asked who he was, she paused.

“You know, it’s so funny,” she said with a mischievous smile. “I don’t remember his name.”

There was no evidence that Williams was operating on less than three hours sleep after playing a 2-hour, 18-minute Grand Slam final the day before. She insisted she felt great, without an ache following the conclusion of the most physically demanding of the sport’s four Grand Slams.

“I felt it more eight years ago,” Williams said. “I’m a little sleepy. But I could go play another three-set, five-set match, if I had to.”

By all accounts, Williams’s competitive hunger, respect for the sport and ambition have never been higher.

In her 20s, she trained sporadically. Her fitness fluctuated. And she competed selectively, whether because of illness, injury or periodic disinterest.

But her own health problems and that of her sister Venus, who was diagnosed with an auto-immune disorder last year that causes joint pain and muscle fatigue, has made Williams appreciate her achievements more.

“It’s not that I didn’t appreciate winning a Slam in 2005,” she said. “But I feel there is way more appreciating now. Each one is going for history.”

That’s a new realization for Williams, who brushed aside questions about her place in tennis history as a younger athlete. But with signs of the fleeting nature of her career all around — the illness that Venus defies each time she competes, the recent retirement of her childhood friend Andy Roddick, and the fact that she’s now within striking distance of equaling the 18 major singles titles won by Chris Evert and Martina Navratilova — Williams is talking frankly about what she wants to achieve before retiring.

“I kind of just started playing for history,” Williams said. “I hope I see it now.”

Squarely in her sights: Three more majors, which would bring her to 18. Or more.

“It’s very motivating,” Williams conceded. “And since I plan on playing for a long time, it’s definitely plausible. I have to make sure I stay healthy and stay positive and stay calm. And if I never win another Grand Slam, I’ve had a fabulous career, an historic career. And I’ve done some major things.”