England manager Martin Johnson said the tense World Cup victory over Argentina had "aged him about 20 years".
Johnson's team only went in front for the first time with 13 minutes remaining as they edged to a 13-9 victory in their Pool B opener.
"That's what World Cups are about," he said. "The ball won't bounce your way and you have to find a way to win.
"We got the win. It wasn't a fantastic performance by any means, but a fantastic win in the circumstances."
England's pack took a long time to get to grips with the grizzled Pumas eight, and it was only in the last quarter of the game that Johnson's men finally got the upper hand, with replacement scrum-half Ben Youngs darting over for the decisive try.
"Youngsy came on and turned the game for us," England captain Mike Tindall told ITV. "We got our tempo going and we got a try on the back of it.
"The one thing I am going to give the team credit for is the way we stuck to our task. We got a win but there is a lot to work on."
Fly-half Jonny Wilkinson, the leading points-scorer in World Cup history and second on the all-time Test points list, missed five kicks at goal, but refused to blame the new ball introduced for the tournament.
"I'm not going to apportion any kind of blame other than that on myself," said Wilkinson.
"I was the one kicking the ball and when I hit them I felt I was hitting them very, very well. It's the same for everyone, it's a case of going back to the drawing board and looking at how we can get better."
England blind-side James Haskell will not make a formal complaint to the citing commissioner despite appearing to accuse an Argentina player of attacking his eyes at a late ruck.
"At the last breakdown I got a bit het up. I got cleared out, I had hands in my face and I think it was just a bit of over-exuberance in the end," said Haskell.
"In the heat of the moment you react as you do. It is nothing really."
Although Argentina earned a losing bonus point, captain Felipe Contepomi admitted the defeat could prove costly to their hopes of reaching the semi-finals of a second successive World Cup.
If all results go as expected, the team that finishes second in Pool B will face New Zealand in the quarter-finals.
"In terms of the result it can cost us dearly because it is always easier if you win your first game," said Contepomi, who will have an X-ray to discover the extent of the rib injury that forced him off.
"In terms of performance the whole team made a big step forward.
"Hopefully we can improve our game. Having played only one Test in 11 months we knew it would be hard but we have to go on from here."
For the latest on the 2011 Rugby World Cup in New Zealand visit our breaking news and gossip page.