We maintain a polite fiction that the meeting was a success.
polite fiction
idiomA social scenario in which all participants are aware of a truth, but pretend to believe in some alternative version of events to avoid conflict or embarrassment.
Everyone knew the boss was fired, but they kept up a polite fiction that he had simply retired.
The diplomatic team relied on a polite fiction to ignore the obvious tensions, allowing the negotiations to continue without an immediate collapse.