be under no illusion
To know and understand the reality or truth of a situation. Don't worry, I'm not getting back together with Alex. After all his lies, I'm under no illusion about how he operates.
be under no illusion (or illusions)
be fully aware of the true state of affairs. 1992 Christian Scientist Monitor It is crucial to the nation's security…that we be under no illusions about reasons for this zero-loss rate.