Jordan Spieth hopes he "never experiences again" the collapse of form that saw him lose a five-shot lead on the final day of the Masters.
The 22-year-old, winner at Augusta last year, dropped six shots in three holes on the back nine, allowing England's Danny Willett to seize his first major.
"It's tough," said Spieth. "I just think it was a very tough 30 minutes.
"Big picture, this will hurt. We still have the confidence we are a closing team. I have no doubt of that ability."
'It feels like we are collapsing'
Spieth, though wayward at times with his driver during the four days, had continued the dominance he displayed in 2015 over the opening 54 holes.
He became the first man to lead the Masters for seven straight rounds and looked set to win a third major after carding four successive birdies to open a five-shot lead with nine holes to play on seven under.
But bogeys on 10 and 11 were followed by a quadruple-bogey on the par-three 12th after both his tee shot and third effort found water.
The American later admitted he turned to his caddie Michael Greller and said: "Buddy, it feels like we are collapsing."
"I put a bad swing on it at the wrong time," added Spieth, who finished tied for second with Lee Westwood, three shots behind Willett.
"It was just a lack of discipline coming off the two bogeys instead of recognising I was still leading the Masters by a couple of shots."
A painful handing over ceremony
Spieth's calamity came 20 years after Australia's Greg Norman lost a six-shot lead in the final round of the Masters, as Willett's compatriot Nick Faldo won the third of his Green Jackets.
The US Open champion eventually turned in a one-over-par 73 on the final day and looked visibly distraught as he presented Willett with the Green Jacket afterwards.
"I can't think of anybody who may have had a tougher ceremony to experience," the world number two told reporters.
"He just said, 'really well played,'" said Willett. "He shook my hand like the true gent he is. He's a class act to be able to hold face like that, hurting like I imagine he would be."
'A life-long memory'
Former US Ryder Cup captain Paul Azinger told BBC Sport: "It's gut-wrenching to watch a player lose a big lead like Spieth has today.
"He will lose a lot of sleep over this. It will stay with him for his whole life. It was almost Norman-esque. Golf can rip one man's heart out and give another man great joy."
Lee Westwood, who secured his best major finish since 2010, said: "It's a fine line between disaster and success and it happened to Jordan. Anything can happen at Augusta."
World number one Jason Day said: "Right now it's unfortunate and I'm sure he's killing himself for it. But we all do it to ourselves. Hopefully he just learns from it and gets better."
Smylie Kaufman, who played with Spieth in the final pairing, said it "just kind of stunk" to watch his fellow American's collapse.
"I was really cheering for Jordan as a buddy, and it's unfortunate what happened... just kind of a weird day for both of us," said Kaufman, who struggled to an 81 to end his first Masters on seven over.