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.
"We got quicker ball in the second half, we wanted space out wide and when we went wide we got turned over a lot," Johnson told ITV.
"We had to keep going. We always thought if we kept going we'd get there."
Relieved skipper Mike Tindall hailed Ben Youngs after the replacement scrum-half's late try spared England's blushes.
Youngs, a second-half replacement for Richard Wigglesworth, darted over after 67 minutes in his first appearance since knee surgery in the summer.
"Youngsy came on and turned the game for us," 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."
England conceded 11 penalties in all and Tindall acknowledged they will have to work hard on improving their discipline ahead of their remaining Pool B matches.
"We gave away three easy penalties early in the game and from then on it makes it hard work for you," he said.
"You've got to play to what you are getting away with and we were not squeaky clean enough. It is something to go away and look at."
Although Argentina earned a losing bonus point, captain Felipe Contepomi admitted the defeat could prove costly to their hopes of reaching the semi-finals for the 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."
