Goals from Ilkay Gundogan and Kevin De Bruyne sealed the Citizens a comfortable 2-0 FA Cup victory over Everton on Saturday.
Despite a slow start to the season, which brought suggestions that Guardiola needed to perform a rebuild to get them back on track, they turned around their season to embark on a 28-game unbeaten run following a loss to Tottenham on November 21.
“We have to adapt - every game is different,” Guardiola said. “Leicester may be similar and play four in the middle. Dortmund and Leeds will be different.
“Managers know what they have to do.
“But when you win a lot of games like we have in the last four months, it’s because you can adapt. That pleases me the most.
“It’s not just tactics, it’s mental - being ready every game.
“What we have done is more than remarkable. It’s incredible. One of the greatest achievements we have done together.
“We haven’t won anything yet, so we will be focused and we will see how far we arrive in the competitions.
"Honestly, since last break four months ago, we played 34 games.
"In this winter time, playing every three days, with incredible commitment in every competition, I don't have any words to express that."
With 10 minutes remaining, Guardiola elected to throw on Kevin De Bruyne as the Citizens were been held on a 0-0 draw.
"At the end, we decided on Riyad [Mahrez] and Kevin and they changed the rhythm a little bit and fortunately, Ilkay Gundogan was in the place he has to be as a striker or attacking midfielder to score a goal,” Guardiola said.
"Sometimes, with substitutions you are 100% sure with what you have to do; sometimes, you have doubts and if you have doubts, you take more time to do it."