A child's mind is generally incapable of sorting out their own problems or finding solutions, especially when it comes to complex emotional struggles. This is normal, and to be expected.
When you're an adult though, and you haven't gained the emotional development you need to work thru your difficulties on your own, you remain dependent lifelong on a therapeutic professional to assist you with even minor decisions that are perplexing to you~ most of which involve feelings of AMBIVALENCE.
Ambivalence is a very normal occurrence among humans. We might wrestle endlessly with whether to do this or that, or not. The defining aspect of ambivalence is, one part of us wants something (or someone) and the other part does not.
There's internal conflict within when this happens, and what makes the decision making part of our process so terribly hard, is we haven't enough genuine ego strength to decide on our own, what it is we really NEED. Dissociation from our feelings and needs very early in life, leaves us with entitlement issues, the crux of which is: "I don't feel worthy or deserving of receiving what I need and want."
This causes a lot of second-guessing when it comes to decision-making, because rather than honoring our feelings and needs and RELYING on our instincts and intuition to help us determine the best course of action, we try to think our way thru life, which seldom brings positive outcomes.
People with BPD traits are essentially children in adult bodies. They're impulsive, and don't think thru potential repercussions of their choices. They merely act on impulse and usually regret it later on, when they've bitten off more than they can chew.
You cannot expect this element in a person to change, until they enlist emotional growth work. Emotional development is the one thing that helps us become circumspect, or anticipatory of various outcomes of our choices, both positive AND negative. A young child does not have this capacity, and neither do Narcissists or Borderlines, because they are each underdeveloped.
When someone with these personality features ends up questioning a decision they've made, they tend to shame or guilt themselves (in hindsight) for having made a mistake~ but the central reason they've encountered an unfavorable outcome, is they didn't have the maturity to think a choice through for themselves in the first place~ they merely acted on impulse!
Underdeveloped people never learn how to expertly navigate their own ship. They tend to episodically re-enter therapy, every time they hit a speed-bump in life that causes them emotional distress.
Both Narcissists and Borderlines are crisis-oriented. Crisis is what helps them feel pain or torment, which is actually enlivening to 'em, because it breaks thru their non-feeling bubble with intense stimulation. When you're empty and dead inside (due to deficits in emotion development), you CRAVE these opportunities~ even if it just means continuing to get involved with emotionally dangerous lovers.
The false-self is highly developed within the NPD and BPD personality. It's grandiose, which means it frequently suffers from delusions of grandeur, and is accustomed to pumping itself with pep talks and various inner narratives, which have nothing to do with authentic ego strength. It dreams of success far beyond its actual capability, and catalyzes prodigious shame attacks for the Self, when those fantasies are not realized.
Every one of us has an ego, but the EGO within Borderlines and Narcissists is like a house of cards, or a structure built at the shoreline on a beach. It has no foundation beneath it whatsoever, to keep it intact during extreme weather conditions, or rising tides.
Emotional growth is essential to help us develop into adults who can problem-solve on our own, and don't have to go running back to a psychotherapist, to help us maneuver out of the corners into which we've painted ourselves, due to our immature choices and decisions.
In short, responsible, SOLID inner work should help you evolve into being a GROWN-UP, who's not only learned to be your own best friend, but your most highly-skilled and trusted therapist, as well.