Joao Pedro and Matt O'Riley struck late as Brighton overcame an early City lead established by Erling Haaland.
Guardiola said afterwards: “I will reflect in these ten days, clear our heads, players come back fit, this is the target.
“When the players come back, I’d like to play the level of the first half.
“Today was a really good first half. 70 minutes was really good.
“I know how we are playing. I won’t convince you. The level we’re playing is really good in certain moments but we are not able to continue for a long time.
“I’m sure when the players come back, they can make some individual qualities on the team and we’ll be back.
“We lost two games in the Premier League. Of course, we have to change and get back to winning.
“When the players come back I have no doubts we’ll be back to the best.
“This is my challenge, I love a challenge. I won’t step back, more than ever I want to do it. We will try again.
“We try to analyse how we perform - four in a row. Okay. The question is how we are playing.
“Bournemouth deserve it, but the games were really good…Spurs, the young lads. There were many positive things in Lisbon and today but we lost.
“It looks like excuses. This is what I feel. When we play bad, I’m the first to say. I don’t have that feeling.”