The hallmark feature of Borderline Personality Disorder is the lack of a solid sense of self. This leads to the extreme mood shifts, impulsive behaviors and difficulties with relationships that Borderlines are known for. Because of the lack of self, persons with BPD have difficulty in relationships and tend to feel either abandoned or engulfed by the other person. I often feel that Borderlines get a bad rap, because people focus on the behaviors and fail to see the underlying pain, disorganization and terror.