Eddie Jones says he cannot explain why England came up short after his side failed to achieve their goal of winning the World Cup in Japan.
England were beaten 32-12 by South Africa in the final in Yokohama.
It came a week after England knocked out three-time champions New Zealand in the semi-final in one of the best performances in Jones' tenure as coach.
"I'm not sure why we came up short today, sometimes you never know," said the England head coach.
"Sometimes you can investigate but you'll never know why it happened. We're going to be kicking stones now for four years, we're massively disappointed."
Captain Owen Farrell kicked four penalties for England, but Handre Pollard replied with six for South Africa before tries from Makazole Mapimpi and Cheslin Kolbe put the game beyond Jones' side.
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The Australian has a contract with England until 2021 but said it was "not the time to discuss" his future after the defeat.
"We are the second best team in the world," added Jones, who lost the 2003 final to England while coaching the Wallabies but was a consultant to South Africa the last time the Springboks won the trophy in 2007.
"We didn't meet our goal to be the best team in the world, but we are the second best team in the world, so I think that's how we should be remembered.
"The players prepared tremendously well for this World Cup. I thought they played with a lot of pride and passion, and we got caught short today.
"These things happen, but we can't doubt the effort of the players. I thought they were extraordinary.
"The only thing I am worried about now is having a few beers, and that's the only thing we will worry about.
"And then after we have a few beers today, we will probably have a few more beers tomorrow and maybe Monday, and then maybe we will have to pull up stumps."
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Defeat 'heartbreaking' for England
England scrum-half Ben Youngs says it will take a long time to get over the defeat.
"We're devastated," he said. "It's been an unbelievable effort, it hasn't just been this tournament, it's been a huge lead-up to this and it's heartbreaking.
"It will take a while to get over this."
Captain Farrell added: "[We're] proud to be a part of it, proud to have come as far as we've come.
"Today didn't go our way but we've enjoyed this tournament and a lot of people have put a lot of work into us.
"The squad has enjoyed its time here in Japan, the competition as a whole. It's been fantastically run and we've loved our time here."
Matt Dawson, World Cup-winning scrum-half in 2003, says it is important to "look after" England's players after the loss.
"The England players will have to be looked after here," he told BBC Radio 5 Live.
"It's a while before they play again in an England jersey. Some will think about whether they'll take it on and go through that again."
'One of the most painful experiences'
Fly-half George Ford says England were "nowhere near good enough" to win Saturday's final, but insists Jones' side "will come back".
"Congratulations to South Africa, I thought they executed their plan brilliantly," Ford told BBC Radio 5 Live.
"I couldn't be prouder of the lads, they've been brilliant all tournament up front, they just did a job on us today.
"It's obviously a huge disappointment for our side. We wanted to finish it off today but we were nowhere near good enough to do that.
"We've come a long way and it's probably the most together squad I've ever been a part of."
|England's World Cup|
|Top points scorer: Owen Farrell (58)|
|Most tries scored: Jonny May, Manu Tuilagi, Luke Cowan-Dickie (3)|
|Most clean breaks made: Anthony Watson (10)|
|Most tackles: Maro Itoje (71)|
Lock Maro Itoje says his England team-mates "are trying to draw positives out of the journey" and is already looking towards the 2023 tournament in France.
"It is not exactly a disco in there," the 25-year-old said about the England dressing room. "But we are united, we are sticking together, we are talking to each other and consoling each other.
"We want to get better and most of this squad will be at the next one. It is a long way away to think about now but our goal is to do better next time around.
"Losing this game was one of the most painful experiences that I have had in life, not just my rugby career. It is not easy.
"It is a tough time and tough period to go through but if we stay together then I am sure all will be well in the long run.
"We are disappointed to lose. Our goal was to win the World Cup and we have fallen short."
'It is special to be a part of this'
Wing Jonny May says it will be "special" to reflect on England's tournament once the dust settles on their final defeat.
"I will keep that [silver] medal and I am sure that once everything calms down and you come back into your own body - it is special to be a part of this - an England player in a World Cup in Japan," he said.
"There have been some great moments. I couldn't have done any more and the team couldn't have done any more. It's just what happened. It has been special to represent our country."
Joe Marler says he was "really gutted" to see fellow prop Kyle Sinckler taken off with concussion in the third minute but believes he will continue to improve along with the rest of the England squad.
"This team, if they keep developing as they have, they will dominate for a long period and that is a joy to see," said Marler.
"I have thoroughly enjoyed my time over the last 10 weeks and seeing the growth of the youngsters. They have got a bright future."