Pep Guardiola admitted he had doubts about his Manchester City side but not his principles after victory over West Brom ended a six-match winless run.
City had not won in all competitions since 24 September but beat the Baggies 4-0 to regain top spot from Arsenal.
“Six games without winning is a long time,” Guardiola told BBC Sport.
“When we lose always you doubt. Also in the second half when we didn’t play like the first half I had doubts about what we had to do to improve.”
He added: “The principles? No doubts. But to know the players, how they play with other ones, how you play in different systems, sometimes you make a doubt, yes.
“Winning again is so important for us. When you lose, the problem is you lose a bit of confidence each time for the next game and it has happened in this period.”
Sergio Aguero scored twice – his first goals in six games – before midfielder Ilkay Gundogan added two more after a brief West Brom revival.
Argentina striker Aguero’s seven goals in the league make him joint top-scorer with Chelsea’s Diego Costa.
BBC Match of the Day pundit Danny Murphy said: “I think it is hard for Aguero to get much better in scoring goals, but he is looking a little bit more dynamic off the ball, closing people down and making runs.
“He was harrying people and that is not something that I associate with the Sergio Aguero of last season. He ran 10.2km today against West Brom. That is a lot different from last season when he was clocking less than eight on average.”
Alan Shearer added: “He is the one genuine world-class player we have in the Premier League.”
“We need Sergio,” Guardiola said.
“We know how important it is for us when he can be as good as he is. He is part of the history of this club but I would like to help him still. That is my target. Help him to feel how important he is for us in in every game.
“He is one of the best. And above all that he is one of the nicest people I have ever met. I love working with the nice guys, and Sergio is one of them.”