The world number one retained her WTA Championships title in Istanbul with a 2-6 6-3 6-0 victory over Li Na at a packed Sinan Erdem Dome.
For much of the week it had seemed inevitable she would walk away the winner, but in the end she had to summon up her last dregs of energy to complete a 78th win from 82 matches this season.
Williams has won more matches and more titles than in any other year of her career, but she could not overlook her quarter-final loss at the Australian Open and fourth-round defeat at Wimbledon.
In 2002 she won three successive grand slam titles before completing the 'Serena Slam' at the Australian Open the following year.
"I live to win slams," she said. "Obviously I'm so excited to be the WTA champion, and I think I have a top three (seasons). I can't say it's the best and I can't say it's not the best."
Williams picked out winning the French Open for only the second time in 11 years as the highlight of her season, but putting right the few bumps in the road that she hit this season is clearly a motivating factor.
The first opportunity will come in less than three month's time when the 2014 season kicks into gear at the Australian Open.
She said: "It's never too far away but there are 128 people that have the same thought that I have. I hope to be the one standing up in the end, and it's for sure my next goal.
"Seeing that I didn't do as well as I wanted to there, actually the past few years. My goal is just to go a year in Australia without twisting an ankle. That's what I'm going to start with."
First, though, comes a much-needed break from tennis, and Williams joked of her racquet sponsor: "I definitely won't be hanging out with my buddy Wilson for a while. We need some time apart, even though I love him."
Although Li ended up on the losing side, it has been a standout season for the 31-year-old from China, who will be ranked a career-high of number three on Monday.
Coach Carlos Rodriguez has helped Li find an impressive level of consistency and also added variety to her game.
"The whole team, we've tried to do what we say and finally we've made it," she said.
"I have a little bit of a bad taste because the last set was to love but I'm still feeling positive. At least in the whole match I used a lot of serve and volley. This is an improvement."
The tournament bade farewell to Turkey and will begin a five-year stint in Singapore in 12 months' time.
Should Williams successfully defend her title, she will have an orchid named after her.
"I love orchids," she said. "That would be really nice."