That’s the whole thing with a mental illness. People who are mentally ill do not understand the consequences of what they are saying or doing. My daughters mother left her in the middle of a Walmart parking lot when she was 4 months old. 4 years later, she still doesn’t grasp the concept of what she did. In her mind, it never even happened, despite the police and paramedics showing up.
If mentally ill people understood what they were saying and doing, then they would be just like you and me, and not mentally ill.