The high point came Saturday on Centre Court at Wimbledon, when Williams dropped down to the grass, hands covering her face. She was all the way back, a Grand Slam champion yet again.
Her serve as good as there is, her grit as good as ever, Williams was dominant at the start and finish, beating Agnieszka Radwanska of Poland 6-1, 5-7, 6-2 to win a fifth championship at the All England Club and 14th major title overall, ending a two-year drought.
"I just remember, I was on the couch and I didn't leave the whole day, for two days. I was just over it. I was praying, like, `I can't take any more. I've endured enough. Let me be able to get through this,"' recalled Williams, a former No. 1 whose ranking slid to 175th after a fourth-round loss at the All England Club last year, her second tournament back.
"Coming here and winning today is amazing," she said. "It's been an unbelievable journey for me."
That's why tears flowed during the on-court trophy ceremony. And why Williams squeezed tight during post-victory hugs with her parents and older sister Venus, who has five Wimbledon titles of her own -- meaning that one pair of siblings who learned to play tennis on public courts in Compton, Calif., now accounts for 10 of the past 13 singles trophies. They added their fifth Wimbledon doubles championship Saturday night, teaming to beat Andrea Hlavackova and Lucie Hradecka of the Czech Republic 7-5, 6-4.
"She hasn't had an easy road. Things have happened in her life that you can't predict or control, so it's hard to be in that situation. Things happen that you didn't deserve," said Venus, who is dealing with an autoimmune disease that can cause fatigue. "For her to fight through that and come back and be a champion. ... It was definitely emotional."
A few days after winning Wimbledon in 2010, Serena Williams cut both feet on broken glass while leaving a restaurant in Germany. She needed two operations on her right foot. Then she got blood clots in her lungs, for which she needed to inject herself with a blood thinner. Those shots led to a pool of blood gathering under her stomach's skin, requiring another procedure.
"That made her realize where her life was, really, and where she really belonged and that she really loved the game," said Williams' mother, Oracene Price. "You never appreciate anything until you almost lose it."
Against Radwanska, who was trying to be the first Polish Grand Slam singles champion, Williams was streaky at times, but also superb. She won the first five games and the last five. She compiled a 58-13 landslide of winners. She swatted 17 aces, including four at 114 mph, 107 mph, 115 mph, 111 mph in one marvelous game to pull even at 2-all in the third set. That was part of a momentum-swinging run when Williams claimed 15 of 18 points, and that quartet of aces raised her total for the fortnight to a tournament-record 102, surpassing her own mark of 89 in 2010; it's also more than the top number for any man this year at Wimbledon.
"So many aces," said Radwanska, whose two-week total was 16, "and I couldn't do much about it."
There had been a moment, ever so brief, when it appeared Williams might let Saturday's match slip away. After she breezed through the first set on a day when the wind whipped and the temperature was in the mid-50s, rain arrived, causing a delay of about 20 minutes between sets.
Radwanska, who has been fighting a respiratory illness and blew her nose at a changeover, quickly fell behind 3-1 in the second set. Right there is where she made a stand.
Williams was playing in her 18th major final; Radwanska in her first. Actually, she'd never won a match beyond the fourth round at a Grand Slam tournament until this week. So she acknowledged being "a little bit nervous in the beginning."
But the interruption let her "cool down a little bit," explained Radwanska, who would have risen to No. 1 in the rankings by beating Williams but instead will be No. 2, behind Victoria Azarenka. "When I was going on the court the second time, I just felt like a normal match. Didn't seem like a final anymore, so there was not that much pressure."
Radwanska played her usual steady game, and Williams began making more and more errors. A string of mistakes -- swinging volley into the net, double-fault, backhand long, backhand into the net -- let Radwanska break to even the match at one set apiece. What appeared to be a rather drab final, bereft of any drama, suddenly became interesting.
"She got a little nervous out there, in my opinion. In the second set, I think she might have thought, `Well, I got this here,"' said Williams' father, Richard.
He also suspected his daughter might have been feeling a twinge of self-doubt connected to her quick exit in late May at the French Open against a woman ranked 111th, Williams' only first-round loss in 48 career major tournaments.
Williams' explanation for her dip against Radwanska?
"I just got too anxious," she said, "and I shouldn't have been so anxious."
Making her Paris performance really seem like an aberration, Williams regained control down the stretch. She won a 16-stroke point with a forehand putaway to get to break point, then went up 3-2 by smacking a big return that left Radwanska flailing at a running backhand.
If Williams is mainly known for her powerful serves and groundstrokes -- she produced 23 baseline winners to her opponent's five -- she also showed off a deft touch, the sort of thing Radwanska specializes in. Ahead 4-2, Williams earned a second break with a well-disguised forehand drop shot, then raised both arms aloft.
"After that, it was: `I can definitely do this,"' Williams said.
While Monday's rankings will have her listed at No. 4, there's no doubt who is at the top of the game right now. Seeded sixth at the All England Club, she beat the women who were No. 2 (Azarenka), No. 3 (Radwanska) and No. 4 (defending champion Petra Kvitova).
At age 30, Williams is the oldest women's singles champion at any major tournament since Martina Navratilova was 33 when she won Wimbledon in 1990.
And Williams sees no end in sight.
Asked Saturday evening what more she could possibly want, she replied: "Are you kidding? The U.S. Open. The Australian Open. The French Open. Wimbledon, 2013."
Seconds later, she declared: "I have never felt better."