The information contained herein is taken from a site, http://bpd411.org, operated by the Turtle Island Center for Family Services. It deals with the trials, tribulations and stresses inflicted by BPD's on those around them, especially those who have a close emotional tie with them. It is not uncommon for BP's to exhibit strong narcissistic qualities, but this blog discusses the poor unfortunates who have to deal with them.
Patients with a Borderline Personality Disorder are literally incapable of seeing things from the other person's point of view and generally insist that any stresses in the relationship come from the actions of the other person, who is then forced to "walk on eggshells" to avoid provoking an outburst of emotional or physical aggressiveness. This becomes an impossible situation because any slight or mild criticism or disobedience is seen by the BP as an ego attack that has to be met with full fury.
The victim in this situation has to maintain an exceptionally high and excessive level of vigilance over both actions and words, as well as extreme caution in some situations and thus we are dealing with a relationship that is both tense and dysfunctional for the tiptoer. The SO of the BPD feels that if (s)he is careful enough then (s)he will avoid provoking that craziness and rage of which the BP is capable of unleashing at the least perceived provocation. The SO feels that there must be some way (s)he can get it "right" so that the relationship can be OK again. The SO is generally told by the BP over and over that any problems are all the SO's fault, and any negative issues in the relationship derive from the SO's behavior. And any self-blaming attitude the SO might have in always vigorously emphasized and reinforced by the BP. And the BP always holds him/herself blameless, and maintains that only the SO needs self-work and therapy.
Vigilance can be a useful frame of mind when one is exposed to real danger (think Hurricane Sandy or jaywalking or being the goalie in soccer or hockey). But if you are forced to maintain a hyper-vigilant state for too long a period of time, and are unable to take needed rest breaks for your psyche, then the perpetual stress will start to wear you down. Paying perpetual vigilance to everything around you leaves you no time to experience any joy or pleasure in your own life, and your own needs for nurturing and true companionship are incapable of being met. Just think of the spouses of alcoholics who end up going to Alanon because their spouses never quit drinking.
We all occasionally walk on eggshells at various times in our life to preserve peace in the family, but that is quite different from being "on" 24/7. When you are always walking on eggshells, you have no time for self-development, receive no positive reinforcement, and your own emotions can be narrowed down. You may limit your choices severely in order to avoid "provoking" an outburst. You might even stop laughing, being playful and telling jokes about funny things in life because your entire vista with this person is grey and black. Your own emotional needs of course are never attended to, so you never feel fulfilled. It is more like walking through a minefield, looking at your BP for any signs of disapproval or incipient hostility and criticism. You may even be fearful that in one of these temper outbursts real physical harm will come to you or the BP or someone else.
You are entitled to peace in your own life. Your triggering his/her rage does not mean that you always make mistakes. Slowly your sense of self-worth becomes corroded and destroyed, and you lose the ability to think clearly for yourself. You start to wonder where your old self has gone, the happy, joyous, carefree self. Walking on eggshells also involves your excusing his behavior towards you because of his childhood trauma, or poor upbringing, etc, none of which you were responsible for. (S)he may also shrink and restrict your social circle, using various excuses. You may become totally subservient in an attempt to ward off further outbursts of rage. And finally you are usually forbidden to talk about this to your family and friends, or to seek out a therapist, because that would be seen by the BP as a betrayal of the relationship.
It is important to understand that the raging is not controllable by you. It is not a response to what you do but to something inside the BP. You did not create his/her state of mind, you are not responsible for the outbursts of anger and rage from the BP, and you certainly can't cure him/her. His/her actions will continue towards you so long as you are there to receive them. And please, please, please never compromise your own safety. "The Devil made me do it" is not a valid excuse for emotional and physical abuse, and certainly has no place in a loving relationship, and in the long run you will be both frustrated and drained.