South Africa captain Graeme Smith admitted his team failed to produce in key moments of the first Test defeat against England in Port Elizabeth.
Smith saw the match slip from his grasp on the final two days
"I think we did well to get ourselves back into the Test match on day three but on day four we let ourselves down again in a crunch situation," he said.
"Days four and five are where Tests are won and lost and they came out and performed much better than us.
"It was always going to be a hard fight from there."
Smith was particularly critical of his team's batting in the second innings, in which the final seven wickets fell for 63 runs.
"It's just not good enough," he said. "We've got to improve on that and we've got to produce some big performances.
"All credit to England's bowlers, I thought they stuck to their guns well and we let ourselves down."
Smith took some comfort from the match, with debutants AB de Villiers and Dale Steyn showing glimpses of promise.
De Villiers hit six boundaries in knocks of 28 and 14, while Steyn bowled Michael Vaughan with one of the finest deliveries seen all year, pitching on middle stump and knocking back off.
"I thought there were some good performances, some of the young guys coming in," Smith said.
"The bowlers did well to fight back from the day one disappointment."
The captain also believes that time is on his team's side as they look to halt England's record eight-match winning run.
"There are a few positives for us, we know what they are and we have to take them into the next Test match.
"A five-Test series offers us a lot of time to come back and it's crucial we play well in Durban in all five days and not just one or two."