The Cherries stunned the champions 2-1 at Dean Court on Saturday.
Iraola later said: “I think it's very difficult to beat City. You have to enjoy it at least today.
“Tomorrow we will start thinking on Brentford.
“But apart from the result, I'm very, very proud of the performance. I think to beat them, I think deservedly, is even more difficult.
“Even if we suffered until the end because they pushed us in the last minutes, I think we deserve this one.
“I think against this kind of opposition, there has to be a moment where not only for your confidence, also for them, they have to start to think that maybe they don't win today because they normally win all the time,” he said.
“So you have to find a moment where they can think, ‘hey, careful’, and obviously when you score first, I think it becomes an uncomfortable game for them.”
He added: "We need close to the 100 from us and probably them not to have the best of their days even then.
“Even playing this game, if they scored the last one from Haaland, you don't beat them because they are so good. But the first part was non-negotiable.
“If we don't play very, very close to our best level it’s impossible.”