Novak Djokovic felt the pain of a third French Open final defeat even more keenly after going into the match in such good form.
Swiss Stan Wawrinka won 4-6 6-4 6-3 6-4 to upset the Serb's hopes of completing the career Grand Slam in Paris.
Defeat also brought an end to the world number one's 28-match winning streak.
"Of course it hurts, especially because it was in the final. I think I have played a great clay-court season, a great Roland Garros," Djokovic said.
"I came to the position to really win this trophy. I was set up and was really in the match and trying to play tactically as I intended.
"But he just found the solutions on the court. This is sport. That's what happens on this level. You have to accept the loss."
|Russell Fuller, BBC tennis correspondent|
|"Stan Wawrinka knew he would have to produce his very finest tennis for at least three sets, and he did just that - in only his second experience of a Grand Slam final.|
|"The backhand down the line winner to seal the decisive break in the fourth set was the most breathtaking of all, but only one example of the array of glorious attacking shots that made even Djokovic look flustered.|
|"The world number one played well enough to have beaten almost anyone, but for 3 hours and 12 minutes, Wawrinka didn't play like just anyone."|
Top seed Djokovic took the first set with a solitary break of serve but was on the back foot from then on as 30-year-old Wawrinka, the eighth seed, fired a total of 60 winners past him.
"It was not easy to stand there as a runner-up again, but I lost to a better player who played some courageous tennis and deserved to win," said the 28-year-old Serb.
"I think I was hanging in there in the second set. I was coming back from some break points down, saving myself, and playing an even game with him.
"But he was the better player in the second so he deserved to win that one, and the third and the fourth.
"All I can do is say, well done. He deserves it."
Djokovic had gone into Sunday's final as a strong favourite after his quarter-final win over nine-time champion Rafael Nadal, the man who beat him in the 2012 and 2014 finals.
And despite being taken to five sets in his last four Grand Slam matches against Wawrinka, he had lost only once to the Swiss in the last nine years.
"Of course I was more nervous than any other match," said Djokovic.
"It's the final of Roland Garros. We both were aware of the importance of this match, and that's why you tend to have these particular situations.
"But, again, at least I'm proud of the fight that I put into this match. I tried my best. It wasn't to be."
Djokovic will now have to wait another 12 months before trying to add the French Open to the one US Open, two Wimbledon and five Australian Open titles he has won.
"I think people tend to create more of a story where it's just me," he said.
"It feels like I'm the only player who wants to win this trophy and nobody wants to win it as much as I do. This is completely untrue.
"Every single player who is here, especially the top players, want to win this trophy as much as do."
Djokovic will next turn his attention to the grass-court season and defending his title at the All England Club, but only after a few days' recuperation.
"My mind is not in London at the moment, really," he said. "I just got off the court and I need some rest. That's all."
|Djokovic's Grand Slam haul|
|Australian Open:||2008, 2011, 2012, 2013, 2015|