Sergio Aguero's 59th-minute penalty at the Etihad Stadium earned City their fourth successive top-flight win on a night when Jurgen Klopp's Liverpool thrashed Watford 5-0 to stay at the summit.
City have now won eight of their previous nine Premier League games - only dropping points once in a loss to Newcastle United last month.
And while Liverpool sent an emphatic message by returning to winning ways in style, Guardiola insists both clubs will slip up across the final 10 games of the campaign.
"We knew it – Liverpool is a top side, we know that," City manager Guardiola told a news conference.
"Now we have a gap with the first two with the third, we're eight points [ahead of Tottenham], nine points for the leader.
"We knew it, 10 games... many things are going to happen.
"I think we are going to drop points, I think Liverpool are going to drop points. We're going to see until the end.
"It's important now to refresh, good recovery and prepare the game against Bournemouth."
City can go back top of the table at the weekend as they face Bournemouth the day before Liverpool meet Everton in the Merseyside derby.
Guardiola's quadruple-seeking side then meet Watford the following week, with the second leg of their Champions League last-16 tie against Schalke and the FA Cup quarter-final at Swansea then on the schedule prior to the international break.
"Hopefully we can make a good performance against Bournemouth and after we have one week to prepare [for Watford], the last game in the Premier League before 21 days without Premier League again and focus on Schalke and Swansea," Guardiola added.
"That's why it's a real final for us against Bournemouth."
West Ham manager Manuel Pellegrini, who won a title with City in 2013-14, was unhappy with City's penalty.
Substitute Bernardo Silva won the spot-kick when Felipe Anderson bundled into him from behind and Pellegrini felt the contact was minimal.
"I'm not happy with the result because it was not a penalty - Bernardo Silva threw himself down when he felt a touch," he said.
"To be generous, it was a little soft. That is too generous really. It was not a penalty, it's a play that happens a lot of times inside the box."