חי בסרט
Another favorite Hebrewism, which translates literally to "living in a movie". It is used to indicate to one's interlocutor that he is so bound up in his own narrative that he has lost contact with external reality. It's a refreshing refrain from the inanity of the counter-claim, that reality is in fact socially constructed, that we must all live our own truths. It is an implicit reminder that no, in fact, we have a shared truth, a shared reality.
We are all susceptible to succumbing to fantasies and delusions, conspiracies and myths. It is the job of our closest friends to ground our thinking in shared reality, to pull us out of the theater of our own minds when we fail to suspend our disbelief.