In such ways the 'personality-disordered' adult has, despite much intellectual development, remained in their heart and morals a toddler-teenager. They have not developed that self-sameness over time, in the form of being a word-keeper, which is essential if there can be something in us in which others can meaningfully be said to trust, something which allows them to then come to know and love us.
Before continuing, let's be clear: everyone has some degree of 'personality disorder'. (The concept of a morally mature adult is an 'ideal type', it is not something which many of us manage to completely realise all the time.) But the degrees vary widely!
Sometimes I met with someone who in their heart knew full well what they were doing, and so who understood that those they called friends really either merely tolerated them or had fallen for their charms and excuses perhaps because they, the friends, tend to see the best in people or tend depressively to see the worst in themselves. But often I met with people who seemed puzzled and hurt by the chaos they created, perhaps because their projections against overwhelming unbearable moral emotions really did succeed in ridding them of a sense of their guilt and shame, i.e. ridding them of a sense of what they had done to deserve their shunning.
Here I share my thoughts as to what someone might do if they find themselves spoiling their relationships in the above ways.
a. Bring to mind a clear sense of what the right thing for anyone to do in any situation is, and always act only according to this general understanding. In this way you can align yourself with the good rather than only with what feels comfortable or rewarding to you. You can then also reap the rewards within yourself of what we call 'adult dignity' - i.e. feeling good because what you're doing is the right thing to do - and can leave behind the childish form of satisfactions which come from getting your way or getting out of something unpleasant. Dignity is not often talked about today, but in truth it is one of the very few valuable forms of self-love. The dignified person can feel good in herself because she knows she is living according to what is right, and this provides the deepest nourishment that the self can have outside of the love of another. The ambition of living a dignified life also helps with what to do when there's not much joy to be reaped in life. It has us ask: well, what can I do, today, to use my talents well, to help somebody, to grow, to discharge my responsibilities; what meaningful options are open to me? So long as we do what we can then, even if there's not much we can do, even if nothing goes our way, we can feel good in ourselves, so long as we are organised by dignity. By living a dignified life we also reap the rewards of the genuine love and respect of others.
b. Be honest with yourself in acknowledging that whilst there are no criteria for what count as: a reasonable or an unreasonable excuse, a legitimate or illegitimate changing of one's opinion or values, respectful or disrespectful talk, etc, in no way does this mean that it is up to you to say what is and isn't reasonable in your own actions! To think in that way - to think that we have some kind of privileged position from which we can inwardly know about the reasonableness or genuineness of our excuses, and some right to insist on what is thereby true of us - is to be what clinically is called a 'narcissist' - i.e. is to adopt the moral stance of the defensive teenager. (To put it philosophically, our first-person authority is a function of the expressive transparency of our avowals to the thoughts and feelings thereby avowed; it is not a function of our either being better informed than others, or getting the final word, about why we act as we do.) The discernment of what is and isn't reasonable cannot be done in a defensive state of mind; it comes along in life as one develops a mature moral sensibility.
c. Develop a moral practice in which you learn to tolerate and even cherish your guilt and shame and feelings of inadequacy. If this doesn't happen then those awful defensive spirals, in which you keep needing to bolster the lie or the denial of blame and to try to push it into others, thereby alienating them and destroying friendships, will flourish. The person with a 'personality disorder' can get stuck in a moral universe in which admitting blame feels dangerous or seems to make one vulnerable in a potentially devastating way. This is after all how it may seem if you were raised by a 'personality-disordered' parent: your guilt will not be forgiven but held against you as a weapon, and so acknowledging guilt will be felt to be foolish, leaving you open to attack. Well, you can choose to stay in such a moral universe if you want, or you can choose to cultivate a different way of moral being, a way of moral being which is compatible with having genuine friends. In a morally mature universe others respect and forgive you precisely when you make genuine apology, and it is in the genuine apology and the forgiveness that proper relationship can be restored and nourished. Moral maturity consists in learning that such vulnerability to being seen as blameworthy is an essential part of friendship. (Going to confession is an example of a moral practice of this sort.) I said 'cherish your guilt and shame'; what I mean is: come to cherish your conscience which gives you such feelings. (I'm not talking about the bogus neurotic inner-critic-derived versions of depressive guilt and shame, but the genuine articles!) Your conscience is your friend because it helps you know when you've done things wrong; it enables you to rebuild and deepen your friendships. And your vulnerability is your friend because it is the condition of possibility of you having meaningful human relationships at all.