Like most defense mechanisms, many people are not aware they are engaging in devaluation and idealization. Its done subconsciously as a way to protect themselves from perceived stress. In borderline personality disorder, devaluation often alternates with idealization.

Why do borderlines self destruct?

Impulsive, self-destructive behavior may be an attempt to ward off rising anxiety related to the fear of being left alone. The flip side of the fear is the hope that a relationship will be completely soothing.

Do borderlines take responsibility?

Diabetic or hypertensive patients are responsible for managing these vulnerabilities, just as people with borderline personality disorder can take responsibility for their behavior while acknowledging the struggles they will face in managing their turbulent emotions and precipitate actions.