Barca beat the Premier League champions 4-1 on aggregate in the round of 16 last season and City have been given an opportunity to gain revenge after drawing Luis Enrique's side at the same stage of the competition 12 months on.
City were still in the League Cup and the FA Cup this time last year, but defeats to Newcastle United and Middlesbrough ended their hopes of winning a domestic cup competition this season.
Pellegrini believes his team could benefit from those losses when they face four-time European champions Barca over two legs, the first of which takes place at the Etihad Stadium on Tuesday.
The City manager said at a press conference on Monday: "I think that last year was different, last year we arrived after playing 19 games in two months and it wasn't our best moment.
"I hope this year we will do it because we are not playing as many games. We are in a good moment, but we have to recognise we are playing against a strong team.
"It is very important to win, and after that to not concede goals. We must fight for possession of the ball and keep it as long as we can."
City looked set to bow out of the Champions League when they picked up only two points from their first four group games, but victories over Bayern Munich and Roma ensured they progressed.
Wily Chilean Pellegrini believes the manner in which City qualified showed the character within the squad.
"We never thought we were out of the Champions League. We had the trust to continue to fight until the end. This team will always try to do it.
"We didn't play well, especially here at home against Roma and CSKA Moscow but our team showed the personality and quality to qualify."
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