Lorraine, Jake's mother, says of him,

He's just a big baby. That's all he is. He's not gonna hurt us. Strangers he'll hurt. Strange women. Outsiders he'll hurt. That's guaranteed. But not us. He knows us.

She creates this fiction about her son because she so badly wants to believe it is true. Jake has shown himself, for his entire life, to be a violent alcoholic, similar in some ways to his father (who walked out on the family), but the reality of this is simply too painful to bear. And so Lorraine finds other ways to justify Jake's behavior.

Jake creates a similar fiction to erase memories that are too painful. He wants to believe that his father died in a plane crash, a military hero, but the reality is that his father died in the street, drunk, having been hit by a truck. When Lorraine tells him that he already knows this, he shouts,

DON'T TELL ME I ALREADY KNOW SOMETHIN' I DON'T KNOW! DON'T TELL ME THAT! HOW COULD I KNOW SOMETHIN' THAT I DON'T KNOW?

But he does know because he was there. Not only this, but, according to Jake's sister, Sally, Jake had masterminded his father's murder by getting him incredibly intoxicated and then challenging him to a race. Jake tells himself lies in order to protect himself from the memories of his father's awful death.

Beth also creates a fiction in order to deal with what has happened to her. Rather than grapple with the fact that the man she loved so much beat her up so badly that it caused her brain damage, she invents a story about her family having had her brain removed. She "shows" Frankie her scar (which is not actually there) and tells him,

No brain. Cut me out. Cut. Brain. Cut . . . Mike did.

It must be less painful to her to think that her family is trying to get rid of her like she thinks they did her grandmother. She says,

They don't say her name now. She's gone. Vanish. My Father sent her someplace. Had her gone.

Rather than blame Jake, who she continues to care for deeply, she blames them.