The Belgium international playmaker provided two assists and ran the show in the International Champions Cup win in Los Angeles on Wednesday.
And Guardiola hopes to witness a similar level of performance throughout the 2017-18 campaign, as City aim to improve on a third-place finish in the Premier League last term.
"Since I arrived I've seen Kevin and when he's in the right mood, optimistic and happy, he makes a performance like this," Guardiola told a post-match news conference.
"It's difficult to find a player with his quality, they're not easy to find. He's a guy who fights, passes, assists, who does many things.
"Hopefully he'll be stable in his mood. If he stays positive like the last three weeks, he's able to do what he wants."
The City boss also praised goalkeeper Ederson, who produced an improved showing after being at fault for a goal in the 2-0 loss to Manchester United last week.
"It's important for him," Guardiola said.
"The way he played today will help him a lot. Soon he will be Brazil's keeper, and that means a lot."