Guardiola saw his perfect start as City boss come to an end at Celtic Park as the home side led on three separate occasions before eventually holding out for a 3-3 draw.
However, despite being forced to come from behind three times - having not trailed at all during his first 10 matches at the helm - Guardiola believes that his side deserved more.
"It was difficult for us. I'm happy with the reaction from the players, it's not easy to score three goals away. I don't know how many chances they had after the third goal. We should have won it," he told BT Sport.
"It's disappointing to concede at the beginning of each half, but that's football. I know how difficult it is here and they started so strong. The second goal was unlucky, and I don't remember any action for them after they scored their third goal.
"It's OK, it's one point, we didn't lose. You always learn. Now we have Barcelona, maybe the best team. We think about Spurs and, after the international break we'll think about that."
City now sit second in Group C with four points from two games.