Barca completed a league double over Real at the Bernabeu last month in an enthralling game that finished 4-3 in the Catalan club's favour.
A hat-trick from Lionel Messi sealed the points in a game which Real had twice led, but finished with 10 men after Sergio Ramos was sent off in conceding the first of two penalties for the Argentina star.
However, Ancelotti's side have the chance for revenge at the Mestalla on Wednesday as Real look to repeat their achievement of 2011 by overcoming arch rivals Barca to win the Copa.
On that occasion Cristiano Ronaldo scored the winner in extra time, but the Portuguese will play no part in this season's showpiece because of knee and thigh injuries.
Despite Ronaldo's absence, Ancelotti is confident in his side's abilities.
"We played very well at the Bernabeu but we made some mistakes," he said. "We did well during 30 minutes; tomorrow we have 90.
"Barcelona had more ball possession in the last few matches. We have to stop them from doing that in order to win.
"We've worked to avoid the mistakes we made at the Bernabeu. We will try to play with our style and identity. We worked all year long to be able to do it tomorrow.
"There isn't a problem with motivating the players. The players have a lot of desire to win."
