Nadal had hoped to finish a glorious 2013 campaign by beating Novak Djokovic in the final of the prestigious Tour Finals at London's O2 Arena on Monday.
But the world number one suffered one of his few painful defeats this year as Djokovic cruised to a 6-3, 6-4 victory.
Yet the 27-year-old was adamant there was no way one loss was going to take anything away from his achievements over the last 10 months.
But since coming back in February he has won 10 titles, including the French and US Opens, and regained his position on top of the world rankings.
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"It's very special what happened this year. For me, the emotions of this year after a tough time have been fantastic," Nadal said.
"All the achievements, all the success that I had this year, I am talking 100 percent honestly now, without my family and all my team it's impossible to do what I did, with so much success and so many special moments.
The loss denied Nadal a place in the record books as he would have become only the second man after Andre Agassi to have won all four Grand Slams, an Olympic gold medal, the Davis Cup and the Tour Finals.
But, asked if he was frustrated to have missed out on such a rare achievement, Nadal said: "No. That's the sport. Seriously, I don't think winning or losing today is going to change my career.