Leinster finished top of the league but Easterby stressed it was silverware that was their ambition.
"It's hard to put something like that to bed, especially as individuals," said Easterby, speaking at the launch of the 2012-13 RaboDirect PRO12 season in Glasgow.
"Leo [Cullen] was talking about how painful it was when he was still on holiday and how his wife was demanding that he start enjoying his holiday and stop thinking about the final.
"But we see it as we weren't good enough and we need to get better and we have to try to work on getting better every single day and do that up to the weekend and try and win that game and then start the cycle over again.
"The real pain was the players. Particularly this year the Heineken Cup was put to bed pretty quickly and doing something unprecedented against the Ospreys was a pretty big motivating factor.
"The players are the ones that put their bodies on the line and they are the ones who were hurting for a long time after that final.
"It will certainly be a motivating factor this season. The fact of it is that we ran out of steam in the last five or ten minutes of the final and that's something we can't afford to do."
Leinster begin their pursuit of their first Celtic League title since 2008, having lost the last three finals in a row, against Scarlets where Easterby will lock horns with a familiar face following the appointment of brother Simon as the Welsh province's head coach.