Easterby said, "Losing that semi-final was horrible. As a sportsman you remember the horrible defeats more than the victories, they stick in your mind more but it makes you stronger.
"We played well on the day but froze in last ten minutes which was so disappointing. It does take you a while to get over as it was one that got away.
"We can put it right this time. We're a different side from then and we've really raised the bar this year. When you beat some top sides like Toulouse and Munster you realise it's an opportunity; it could be our year."
The Scarlets watched Welsh rivals the Ospreys be mauled by the Tigers in last Saturday's thrilling EDF Energy Cup final at Twickenham, but Easterby insists they saw enough to end Leicester's hopes of an historic treble.
He said: "Leicester are good at getting head and squeezing life out of you so you must make sure you're competitive from the off. The Ospreys made mistakes but they also showed the damage you can do if you get quick ball and run at them.
"It will be hard for Leicester to play another big game so soon but they will take confidence they won that game."