Pep Guardiola's City claimed derby honours and an 11-point lead atop the table with a 2-1 victory at Old Trafford on Sunday.
City benefited from two set-pieces, Nicolas Otamendi scoring the winner after Marcus Rashford cancelled out David Silva's opener, as the Blues sealed a record-equalling 14th win in succession in the Premier League.
Speaking afterwards, City's Belgian star De Bruyne said: "Lots of teams lost points this weekend so it is a big one for us [the win] just to put more pressure on the rest.
"We have to enjoy it and then focus again for Wednesday [against Swansea City].
"It is a big gap. If we slip up we are still in the lead. We can't be complacent. We need to do what we have all year.
"I prefer to be 11 points ahead than 11 points behind, that's for sure."
Asked if he was pleased with City's performance in the derby, De Bruyne added: "If you come away with a 1-0 lead, yes — at 1-1, no.
"That's the way it goes. There were two teams with a lot of quality. It was a nice game to watch with the intensity and the duels. A real derby."