play, always pushing each other to the limit. That's the beauty of our matches and our rivalry in the end."
Djokovic fell to 6-6 in Grand Slam finals with four of them at the US Open, including in 2007 to Roger Federer and last year to Andy Murray. He also lost the 2012 French Open final to Nadal and this year's Wimbledon final to Murray.
But he did win his fourth Australian Open crown in January.
"I wish I won at least one title more, considering the fact I played two finals," Djokovic said. "All the matches I lost, even the French Open, I had that match. I lost it again in semis.
"Overall, it was again a very successful Grand Slam year for me. That's something that I always try to have in the back of my mind."
Djokovic was undone by 53 unforced errors, the most critical in the third set when he let momentum slip out of his hands.
"It's all my fault," he said. "I made some unforced errors in the crucial moments with forehands and dropped the serve twice when I should not have. All of a sudden it's two sets to one for him. Then he started playing much better after that and I obviously could not recover.
"In the important moments he played better tennis and that's why he deserved to win. I was supposed to use the opportunities that were presented to me and I didn't do it. I didn't deserve to win in the end."
But Djokovic doubts he has seen the last of Nadal, whom he rates among the game's greatest of all time.
"Well, 13 Grand Slams for a guy who is 27 years old is incredible," Djokovic said.
"What he achieved so far in his career is something that everybody should respect, no question about it. He's definitely one of the best tennis players ever."