I am a Sagittarius Sun/Mars.
BUT i have a Scorpio Stellium..my venus, mercury, jupiter, pluto and other planetary/asteroid aspects.
MY MOON(emotions)-Taurus.
I also would like to mention-Saturn freezes/blocks whatever it touches.
And Chiron-wounds whatever it touches.
For example- You have your 1st house/The Ascendant. This includes your personality, your natural demeanor, and outlook on life. Whatever may effect that beginning of life can hurt later.
Psychologists state, "What trauma is in our childhood will affect us into adulthood."
Now if Saturn..is in your 1st house, I could see it freezing/blocking that first part of life. Maybe abuse, you didnt have a 'normal' childhood, you moved a lot and couldn't adjust, or something similar.
Most people with Borderline Personality Disorder have had abuse in their childhood.
I would think anyone with an aspect that damages or wounds the 1st(your self), 4th(family life), possibly 7th(marriage/partnerships/relationships), and definitely your 8TH House(sexuality/transformation/psychology/addiction) would suffer from something related. The 12th house(subconscious/fears/deep emotions/Triggers)
Now look at the rulers of these and some of their traits...
-1st house- Ruler: Aries/Mars(Aggression)...Impulsive, aggressive, restless, motivated, very driven, and open to new experiences.
-4th house- Ruler: Cancer/Moon(Emotions)...Family-oriented, emotional, sensitive, intuitive and possessive when it comes to the few you love.
-7th house- Ruler: Libra/Venus(how you Love)...Socially inclined, narcissist at heart, You help mend/combine relationships, natural eye for beauty, gift of making others feel important.
-8th house- Ruler: Scorpio/Pluto(Transformation)...Emotional, Passionate, Persistant, very strong-willed(especially how others see you), but on the inside is a whole other turbulence. It's like a layer upon layer, upon boxes inside a Labyrinth.
-12th house- Ruler: Pisces/Neptune(Delusions/Deceptions)...Intuitive, Very Changeable/Moody, Imaginative, Enormously influenced by surroundings,You look for good in others mostly because you dream of a perfect world.
Now think of all of those above^^^And how someone with Borderline Personality is. I would say all of those can be associated with this disorder.
BORDERLINE PERSONALITY DISORDER TRAITS-(some with an Astrological sign and an Example)
Extreme reactions—including panic, depression, rage, or frantic actions—to abandonment, whether real or perceived..
(ARIES..rage/frantic actions, CANCER-family/friends gone, LIBRA..no socialization, PISCES..real or perceived thoughts)
A pattern of intense and stormy relationships with family, friends, and loved ones, often veering from extreme closeness and love (idealization) to extreme dislike or anger (devaluation)
(SCORPIO..turbulent storm of emotions/no one proving their worth/trusting, CANCER/LIBRA..family-relationships, PISCES..when they realize the person of their dreams isnt that great, ARIES..why they are usually alone/lead others until they betray them)
Distorted and unstable self-image or sense of self, which can result in sudden changes in feelings, opinions, values, or plans and goals for the future (such as school or career choices)
Impulsive and often dangerous behaviors, such as spending sprees, unsafe sex, substance abuse, reckless driving, and binge eating
(ARIES, CANCER, LIBRA, SCORPIO, PISCES..pick your poison
)
Recurring suicidal behaviors or threats or self-harming behavior, such as cutting
Intense and highly changeable moods, with each episode lasting from a few hours to a few days.
(WATER SIGNS...CANCER, SCORPIO, PISCES..and a dash of hot-headed ARIES)
Chronic feelings of emptiness and/or boredom
(ARIES..restless spirit/must-do-something attitude, SCORPIO/PISCES..depths of dispair/no one loves me/they dont understand me)
Inappropriate, intense anger or problems controlling anger
Having stress-related paranoid thoughts or severe dissociative symptoms, such as feeling cut off from oneself, observing oneself from outside the body, or losing touch with reality. (PISCES..but all of them are in this one..just depends which gets to them)
(Traits are from this site listed below)
http://www.nimh.nih.gov/health/topics/borderline-personality-disorder/index.shtml#part_145389
AND that is my explanation!!! Enjoy