City reached at least the quarter-finals of the Champions League for seven straight seasons between 2018-2024, but were eliminated from the competition in a 6-3 aggregate playoff defeat by Real Madrid in February.
The Premier League side have also endured a sub-par season domestically and sit fifth in the standings, 21 points adrift of leaders Liverpool.
With Chelsea and Aston Villa just one point behind City, Guardiola's side will need to be at their best in the final stretch of their league campaign to finish in the top five and earn a spot in the Champions League.
"Of course it is motivation, yeah. I don't think it's a bad thing to be fighting to qualify for the Champions League...," Guardiola told reporters ahead of a trip to Everton on Saturday and a home meeting with Villa on Tuesday.
"It's in our hands, and of course, Goodison Park and Villa are massively important. We don't have much time. I enjoyed (this week's Champions League) games, really nice games. I enjoyed it, I miss it, of course, but I accept that.
"Sometimes in sport you don't perform well, don't deserve to be (there). Hopefully next season we can be, dealing with the big clubs in Europe and challenging them better than we have done this season, what we have done in the last seven years. I take it in that way."
City next face 13th-placed Everton at Goodison Park, where they will be without striker Erling Haaland and goalkeeper Ederson, who was taken off in a 5-2 comeback victory over Crystal Palace last week with a groin injury.
"Next games, he (Haaland) will not be ready. We don't know how long he (Ederson) will be out for," Guardiola said.
"(Manuel Akanji and Phil Foden) came back - Phil just on Thursday, and today with his second session since Old Trafford. And Manu, he made two or three sessions with us, and I see him moving really well.
"(John Stones and Nathan Ake) not yet (back). They're getting better, but not yet."