Without directly accusing the previous Fianna Fail-led governments of damaging Ireland's reputation in Europe, Ms Day did concede there would be a positive response in Brussels to "an effort to re-engage" by the Fine Gael--Labour coalition.
"The perception in Brussels was that the more prosperous Ireland became, the more arrogant Ireland became and the less it felt it needed to invest in all of these things," she said.
"And we had become very successful over the previous 30 years in building up all of this. It shouldn't only be a fair weather relationship.
"Now Ireland needs Europe and Europe is there for Ireland. But people also expect just a little bit of personal investment in the whole thing."
Ms Day, who is herself Irish and is the highest-ranking civil servant in Europe, said that since the new government came into office there had been an "effective communication" that it had a different approach to Europe.
"From the Taoiseach down, there is a strong determination to engage very actively, very comprehensively in everything that the Union does. And I think that is very necessary because Ireland's image in Europe: the shine has gone off it.
"But also I think people here have been looking slightly more quizzically at Europe and there needs to be much more information about what is going on.
"So much of the agenda is so relevant to Ireland but Ireland also has to be part of shaping the agenda," she said.
Ms Day said the European financial crisis was "a crisis of individual countries in the euro but not the euro".
She said the issue of burden-sharing with bondholders was down to the European Central Bank to decide.
But Ms Day backed the banking plan, as part of the wider EU-IMF bailout and recovery programme for Ireland.
"The best expertise in the world has come to the conclusion that this is the best way. And my colleagues, who are much closer to the numbers . . . are very confident in saying this is sustainable.
"And I think it is very important now for Ireland, but also for the whole euro area to say, okay we have now solved the Irish problem . . . it's done, the banks have been restructured, they will be able to lend again," she said.