The trite answer is that everything is true but none of it happened. It is emotionally true, but the events, the plotting, the narrative, isn't true of my life, though I've experienced most of the emotions experienced by the characters in the play.
Patrick MarberAlice: It's the only way to leave. "I don't love you anymore. Goodbye." Dan: Supposing you do still love them? Alice: You don't leave.
Patrick Marber