Hi Lien,
Your question made me think of another thread I posted on recently which was kind of the same idea as what you are talking about... .what is "normal" vs "mental illness" and how do you define it.
Below are the criteria for BPD and it could be argued that nonBPD people demonstrate some of these behaviors... .having anxiety for example, who doesn't have anxiety at one time or another.
Frantic efforts to avoid real or imagined abandonment
A pattern of unstable and intense interpersonal relationships characterized
by extremes between idealization and devaluation (also known as "splitting")
Identity disturbance: Markedly or persistently unstable self-image or sense
of self
Impulsive behavior in at least two areas that are potentially self-damaging
(e.g., spending, sex, substance abuse, reckless driving, binge eating)
Recurrent suicidal behavior, gestures, or threats, or self-harming behavior
Emotional instability in reaction to day-to-day events (e.g., intense episodic
sadness, irritability, or anxiety usually lasting a few hours and only rarely
more than a few days)
Chronic feelings of emptiness
Inappropriate, intense anger or difficulty controlling anger (e.g., frequent
displays of temper, constant anger, recurrent physical fights)
Transient, stress-related paranoid ideation or severe dissociative symptoms
I've often thought with all of us our best traits can become our worst traits if taken too far. Compassion is wonderful until you forget to take care of yourself, Responsibility is great but if taken too far you can miss out on spontaneity, Being brave could become recklessness etc.
To me Personality vs Personality Disorder has to do with how extreme the behaviors become and are they negatively impacting the person's life and the lives of those closest to them.
This is the thread I spoke of above if you want to check it out... .
What is the difference between a BPD relationship and just a "bad" relationship?
https://bpdfamily.com/message_board/index.php?topic=329626.msg13005396#msg13005396Panda39
ISFJ
https://www.16personalities.com/isfj-personality