City suffered another setback, their seventh loss in the last 10 games across all competitions, with a disappointing 2-0 defeat at the hands of Juventus.
Second-half goals from Dusan Vlahovic and Weston McKennie at the Allianz Stadium left Guardiola's side languishing in 22nd place in the standings.
With just two games of the league phase remaining, a place in the top eight and automatic last-16 qualification looks beyond City and they face a battle just to stay in the top 24 and claim a play-off spot.
City manager Guardiola said: "Of course I question myself but I'm stable in good moments and bad moments.
Trending"I try to find a way to do it. I'm incredibly honest. If we play good [I say] we played good and today I thought we played good.
"Our game will save us. We can do it. We conceded few chances compared to the Nottingham Forest game that we won. We're making the right tempo.
"We missed the last pass, did not arrive in the six-yard box [at the right time] or have the composure at the right moment.
"But I love my team. This is life, it happens. Sometimes you have a bad period but I'm going to insist until we're there."
City now face a crunch trip to Paris Saint-Germain, who are also at risk of failing to qualify, next month before closing with a home game against Club Brugge.
Guardiola accepts the top 24 is now the only aim.
He said: "It's the target. We need one point or three points. We go to Paris to try to do it and the last game at home."
Veteran midfielder Ilkay Gundogan said after the game he felt City were suffering from a loss of confidence, but Guardiola dismissed his player's comments.
"I am not agreeing with Ilkay," he said. "Of course it is tough but, except one or two games in this period, we've played good."
City now face a further test of their resolve as they host rivals Manchester United in a derby on Sunday.
Gundogan told TNT Sports: "It [confidence] is a big part of it. That's a mental issue as well.
"You can see that sometimes we miss the ball or lose a duel and you see that we drop immediately and lose the rhythm. They [the opponents] don't even need to do much, but it has such a big effect on us right now. They are able to break our rhythm with the smallest thing.
"Even more you have to do the simple things as good as possible and create and fluidity, then it's work hard again. This is how you get confidence back - do the small and simple things, [but] in crucial moments at the moment we are always doing the wrong things."
Juventus coach Thiago Motta was pleased with the hosts' performance, which boosted their hopes of making the top eight.
"It was a deserved victory," he said. "We had to defend as a team and be ready to attack with quality.
"We have shown we can compete at this level and now we have to do it consistently."