It was another side to Roger Federer, a side the supremely confident master of his trade rarely shows to the outside world. In his moment of victory at the Barclays ATP World Tour Finals at the O2 Arena on Sunday night you could see that Federer's emotions were running high. Later in the evening he talked about the doubts that had been going through his mind in recent times and explained why winning the year-ending championship for a record sixth time, passing the totals of Ivan Lendl and Pete Sampras, meant so much to him.
Federer has not added to his collection of 16 Grand Slam titles for 22 months and his loss at the All England Club this summer to Jo-Wilfried Tsonga, the man he went on to beat in Sunday's final, was a particularly painful blow, especially as it had followed defeat to Rafael Nadal in the final of the French Open.
After going on to lose to Novak Djokovic in the semi-finals of the US Open after scorning two match points, Federer decided that it was time to take a break.
At the end of the first Grand Slam season for nine years in which he had not won one of the sport's four great prizes, the former world No 1 took six weeks off to spend time with his coaches, Paul Annacone and Severin Luthi, his fitness trainer, Pierre Paganini, and his wife, Mirka. When he returned at the start of this month he went on to win three tournaments in a row, at Basle, Paris and finally London, to end the year on a 17-match winning streak.
"I think it's a mental thing," Federer admitted on Sunday night as he explained what had made a difference in recent weeks. "Sometimes it's also the player playing better than you. Jo played better than me at Wimbledon. Maybe not much, but enough just to come through.
"Same as Rafa at the French Open in the final, Novak in the semis of the US Open. It's fine to respect that. But I feel when it happens maybe that often, I do have to question myself, that maybe I did something wrong.
"I think I'm mentally good right now. That was also one of the reasons why I did take some time off, to actually think it through, to get into the right mental mindset. I don't want to say we underestimate or overestimate the mental part of the game, but there is a lot of time that goes by out on tour, during a match, when you're just trying to stay positive, but you can't always be positive out there. It's just too difficult.
"That's where maybe the doubts were just a bit too strong during certain important moments. I don't think I had those doubts for the remainder of the season, which is what I wanted to get out of my system during this six-week break, and I was able to do that."
He added: "For me it was important to step back and have that bird's view from up top and say: 'Where am I right now in my year? It's been a good year. I know I've been playing well, I've been healthy. When is all this hard work going to pay off?' I just had to stick with it and have the right mindset, which I then obviously had when I came back."
The transformation has been remarkable. There have been times in the last month, especially during his remarkable 59-minute destruction of Nadal at the O2 Arena last week, when Federer has looked back to his very best.
When he said earlier this year that regaining the world No 1 ranking remained a target, there cannot have been many within the game who believed it possible. Now that thought might not be so fanciful, especially as Djokovic, the current No 1, has a mountain of ranking points to defend next year.
Federer reclaimed the world No 3 position from Andy Murray yesterday and nobody has finished the season in better shape. Djokovic and Nadal in particular have looked worn out by their efforts earlier in the year.
With the start of the Australian Open less than seven weeks away, it remains to be seen whether the world's top two can rediscover their form and fitness in time for the year's opening Grand Slam event.
Federer said he had never finished a year so strongly and was especially pleased with the way he had closed out Sunday's victory over Tsonga after the Frenchman had levelled the match by winning the second set tie-break.
"I think that was the difference to other matches this year, where I lost so closely," he said. "This time around I was still able to find a way through. I think that was the difference at times during the year, which didn't maybe make this an absolutely phenomenal year."
He added: "I had to go through the third set, which was tough, but eventually I made it. It probably felt even better going through three sets. The relief was amazing. The joy, of course, as you can imagine, was great."
Federer said he was excited about his prospects for next year and thought more Grand Slam titles "might be around the corner", though he also said that much would depend on the three other players in the world's top four. "Novak was the player of the year, which goes without saying," Federer said. I thought Andy Murray played a very good season this year. It was just unfortunate he couldn't finish here strong. Other than that I thought he's going to be very tough to beat next year. And Rafa with his class anyway, he's always going to be a threat for the throne, to win all the big tournaments."
Federer, who is not usually one for false modesty, said he was "extremely happy and extremely proud" to have won more Grand Slam titles and year-end championships than any other player. "I still don't feel like I'm better than Pete Sampras, or Lendl for that matter," he said. "I still believe they are two of the all-time greats to play the game. I'm just happy to be compared to them."
Age is no barrier: Three golden 'oldies'
He turned pro in 1980 and performed well on tour for years but it took him until the age of 41 to win his first major, winning two in one season. At 54, he is on the seniors tour.
He was included in the England squad in 1999 but it took him until 2008 to make his Test debut. Now 32, he has since helped England win the Ashes and T20 World Cup.
She ran in the 2010 European Athletics Championships aged 50. Her best Olympics was in 1996, winning two medals. She also won silver in the 4x100m relay aged 40.