Manchester City hold the advantage in the tie, after winning 5-3 in the first leg at the Etihad stadium.
Guardiola believes the only way to beat Monaco, who has scored 123 goals in all competitions is to score goals.
“Even when I was at Barcelona and Bayern Munich I could not assure that we would win that Champions League,” he told a pre-match news conference.
“In that way [attacking] is the only way it can happen. It is the only way I know
“Monaco play to attack, our team play to attack. I’m pretty sure it is going to be a fantastic game.
“When a team scores 123 goals it is because they are able to score in many, many different ways.
“The best way [to beat them] is scoring goals – take the ball and attack as much as possible is the only way to play this kind of team.
“If in 90 minutes you are thinking about 5-3, you kill yourself.”