England coach Stuart Lancaster refused to get carried away after watching his side revive their Six Nations title hopes with a dominant 20-0 Calcutta Cup win away to Scotland on Saturday.
And he warned England would need to improve when they face Ireland at Twickenham on February 22.
Ireland have won their opening two Six Nations matches, beating Scotland 28-6 and defending champions Wales 26-3.
The 132nd edition of rugby union's oldest international fixture was also one of the most lopsided, with a dire Scotland failing to score a point against England for the first time since 1978.
Yet although England scored tries in Edinburgh through centre Luther Burrell and fullback Mike Brown, they also botched several opportunities in a second half where they managed just seven points.
"We were pleased with a lot of aspects, but are frustrated that we didn't convert more of our opportunities, because we dominated the second half," Lancaster said.
"There were chances there that we didn't take and we definitely have regrets over the points we left out there."
However, he added: "We played some really good stuff in difficult conditions. Scotland had to defend desperately."
Burrell's try was his second in as many Tests after his effort on debut in England's 26-24 loss away to France in Paris and Lancaster was pleased by his evolving midfield partnership with Billy Twelvetrees.
"The work that (assistant coaches) Andy Farrell and Mike Catt have done with Luther and Billy is really paying off," Lancaster said.
"They'll need to be on top of their game against the Irish centres (Brian O'Driscoll and Gordon D'Arcy), who are clearly world class."
