City meet West Ham on Saturday, having won just twice in their past 14 games.
Guardiola said on Friday: "There are many, many things (involved in being a manager) and I missed something - something I am not doing well.
"In the end, when you lose a lot of games it is an incredible responsibility for the manager to take. There is something the team needs and confidence and I was not able to do it.
"The call is on me first, it's not the players. They naturally drop a little bit and that is normal. It happened a little bit last season as well.
"With this consistency (of results) I should have found it, and that is why we're in this position.
"I blame (myself). It's not to say, 'oh how nice is Pep' - it's the truth. I lead that group of players and I could not lift them. This is the reality."
Guardiola also said: "We were the only unbeaten team in Europe (until 30 October) and top of the league, but immediately we went down, for injuries, many things we've talked about.
"But, even with that, I should have found a way to get better results."