O'Neill does not expect there to be any hangover after Villa's second defeat of the season at Wembley in last Saturday's FA Cup semi-final against Chelsea.
Villa, also beaten at Wembley in the Carling Cup final by Manchester United, have become outsiders in the race to finish fourth after slipping eight points behind Manchester City.
But the clash with Everton on Wednesday is their game in hand on City and O'Neill said: "After the disappointment of the weekend we just have to get on with
the games to come. You cannot bring things back. It's gone.
"The players are very upbeat.Naturally, they are disappointed but they have to get over it.
"We have an opportunity against Everton to win a game and put ourselves back into contention.
"It hasn't been difficult to lift the players. We know that as days go past things begin to fade.
"The players are frustrated at what happened against Chelsea but we are totally focussed on trying to beat Everton.
"Our experiences at Wembley have been unfortunate but it will not stop us wanting to go back again next season.
"There is still plenty of motivation about the team and while there is life there is still hope.
"We are now down to a six game season and I am sure the players will show in their play that there is loads to play for."
But O'Neill knows that Villa will face a severe test against Everton who have their own aspirations of securing European football next season following their impressive run of form in 2010.
"Everton are creeping up and looking for a European place," admitted O'Neill.
"Perhaps they may think the fourth place is beyond them because they don't have enough games to play and they are too many points behind.
"But certainly European football is within their midst.
"We have not been out of the top seven all season and we want to stay there and the only way you can do that is to win some football games. There is none bigger than the Everton game."
O'Neill is full of praise for the job that Everton manager David Moyes has done at Goodison Park.
The former Celtic boss said: "David has been at Everton for eight years
and when he went there things at Goodison could have been better.
"It has been a fine club in the past but it needed guiding, it needed resurrecting and he has done exactly that.
"In one season they finished fourth to get into the Champions League and they remain the only club to have broken the mould of the top four.
"David is certainly gathering a team together and they are getting a bit of strength and depth about them with some very fine players coming through.
"I see all that and David will be the first one to tell you that it takes a wee bit of time.
"This is my fourth season at Villa and I think we have some really fine players who are developing and that is very pleasing.
"But everyone is craving instant success, including myself, and it would be great to have it.
"Overall, the team is improving and I am very pleased with the attitude of the team, pleased with the results they have tried to get this season and the very fact they are still contesting at this stage of the season speaks volumes for them."