The reigning European champions squandered a two-goal lead to eventually lose 3-2 to Manchester City at the Allianz Arena and although it was a negative result, the Spaniard was not getting too downcast, especially after the visitors put in a top show after conceding twice early.
"When you play in Europe and you play against good teams like Manchester City, always this situation can happen," he told Sky Sports.
"You have to accept this defeat and understand how difficult it is to come back and to play good."
The loss was the first in proper competition since March when they were beaten at home by Arsenal in the Champions League and their first defeat since the end of July when Borussia Dortmund had them in the German Super Cup.
On the back of a 40-match unbeaten streak in the Bundesliga, Guardiola felt perhaps it was not such a bad time for his side to lose.
"Perhaps we needed a defeat to remind us of a few things," the former Barcelona boss added.
"We have made a good start in the league, in the cup, in the Champions League, winning in Manchester, perhaps we thought things were too easy.
"Congratulations to City, I also congratulated my players in the changing room for finishing top of their group.
"The most important thing now is that we learn the lessons from the defeat."
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