Borderline Personality Disorder: An essential feature of this disorder is a pervasive pattern of instability of self-image, interpersonal relationships, and mood, beginning in early adulthood and present in a variety of contexts. A marked and persistent identity disturbance is almost invariably present. This is often pervasive, and is manifested by uncertainty about several life issues, such as self-image, sexual orientation, long-term goals or career choice, types of friends or lovers to have, and which values to adopt.

Girl, Interrupted (1994)