Barca played Arsenal off the park with some breathtaking football in the first half at the Emirates Stadium last week and went 2-0 up early in the second period.
The Catalans were eventually pegged back, though, and had to settle for a 2-2 draw as Arsenal rallied late on.
It was perhaps an unfair reflection of the play, which Barca dominated, creating 22 chances overall and an incredible 11 in the first 15 minutes.
But Guardiola says a repeat of that performance cannot be expected tomorrow.
"What we did the other day has nothing to do with tomorrow's match," Guardiola said. "I am not expecting a first 15 minutes like we played in London or a game with 22 chances for us, that doesn't happen often in the Champions League.
"Those things only happen every now and again and it's in the past. We have to forget about it and focus on doing our job tomorrow."
Guardiola also warned his players that anything other than a professional performance could see his side knocked out of the competition.
"We performed well last week but now we have to go again and if we don't play well, if we do not produce the necessary level of performance, it will be tough and we might not get to the semi-finals," he said.
Guardiola does not believe Arsenal have gained the initiative following their late comeback in the first leg.
"I don't know what my players have in their mind and I have no idea what Arsenal's players are thinking, but are they in a better condition that us? I don't think so," he added.
"Tomorrow is a final, it's our most important game of the season and we have to treat it like a final."
Guardiola is missing a host of first-team players for tomorrow night's clash, with defensive pair Carles Puyol and Gerard Pique suspended.
Zlatan Ibrahimovic, who scored Barca's goals at the Emirates, is also out after picking up a calf injury in the warm-up ahead of Saturday's 4-1 win at home to Athletic Bilbao.
"It's bad news because he is a very important player for us, so we hope he recovers as soon as possible," Guardiola said.
The Barca coach will also make a late decision on Andres Iniesta, who is out with a thigh problem but is now back in full training.
With Ibrahimovic missing, Guardiola has a straight choice between Thierry Henry and Bojan Krkic for the centre-forward position.
And he has given his backing to Henry, who was criticised this week for a supposed lack of commitment following the game in London, when he appeared keen to salute Arsenal's fans and was very disappointing in his 20-minute cameo.
"Henry's commitment is often doubted but I can't understand that," Guardiola said. "He is always committed and he would not still being playing among the elite at 33 if that were not the case.
"He has had some problems with his tendons, but I hope for the best from him."
Henry looks likely to start on the bench, however, after Bojan starred in Saturday's 4-1 win against Bilbao.
The youngster scored twice and Guardiola is happy with the homegrown striker.
"The goals have given him a lot of confidence, but beyond that we are happy with everything he brought us (on Saturday). He is in good form and that's a great sign," he said.
And Bojan himself hopes for an opportunity on the big stage.
"It's a great match in a precious scenario to be enjoyed. I would like to play but there are a lot of top players here and the coach is the best person to decide," he said.
"The other day I played a great game and there is a chance to play tomorrow, so if I do I will give my best and try to take it.
"But the important thing is to win the game."