Stand-in captain Kumar Sangakkara rued Sri Lanka's bizarre batting collapse in the first Test after his team lost the three-match series 1-0 to England.
Sangakkara's six-hour 119 helped clinch a draw in the third and final Test at the Rose Bowl on Monday as his side finished on 334 for five, 141 runs ahead of the home team.
The remarkable innings defeat in the opening Test in Cardiff -- where Sri Lanka were skittled for 82 in 24 overs -- ultimately cost them the series.
"That was probably the biggest regret on this tour," Sangakkara told reporters. "None of us were switched on to that situation.
"We needed to bat consistently for 25 or 30 overs, just one pair to put on a proper partnership on a wicket that was flatter than this one.
"It goes to show that one mistake, two mistakes, can magnify a situation that we should have been capable of handling nine times out of 10," added Sangakkara who was skippering the side at the Rose Bowl in place of the injured Tillakaratne Dilshan.
England's series victory was their fifth in a row but Sri Lanka are clearly missing retired spinner Muttiah Muralitharan.
Sangakkara said his team had to find new ways of winning now that Muralitharan and pace pair Chaminda Vaas and Lasith Malinga had quit the Test arena.
"Our ambition has to be to consolidate with the players we have, the ability we have, and find new ways of winning Test matches," he added. "We don't have Muralitharan any more, we don't have Vaas.
"For us to win we have to find different avenues. Those are the questions we need to answer in the months ahead."
It is a more optimistic outlook for captain Andrew Strauss's England, who are eyeing the world number one Test ranking.
Strauss's men are now third behind South Africa and leaders India, who tour England next month.
"We'll take the series win -- it continues our momentum from the winter and leads us into the India series in good cheer and in pretty good form," Strauss said.
"All three Test matches were affected by the weather and in all three Tests time was running out in order to force a result. In a way we're very satisfied we were able to convert one of the three opportunities to force a result.
"Maybe there's a tinge of disappointment we weren't able to do more today because we felt we were in with a really good chance of winning the game," added Strauss.
Both teams must now switch their attentions to Saturday's one-off Twenty20 international at Bristol and the subsequent five-match 50-over series.
Sri Lanka should have Dilshan back after he missed the third Test with a broken thumb.
"I think Dilsh will be fine," Sangakkara added, praising the captain's 193 in the drawn second Test at Lord's. "We hope he will be fit because of the way he is batting.
"I think he'll again be the key factor for us to win the ODI series. For him to be back leading us on the field will be good for all of us and Dilsh."