Thus, any therapy has to allow for these phenomena. Borderlines need to be medically stabilized so they can think better and be amenable to therapy. Otherwise, it is like talking to a diabetic to get their blood sugar down. Borderlines are very logical in what they do, since their symptoms flow from their biochemistry. To change the aberrant behaviors, you need to change the chemistry, and then do therapy.
Narcissists are close to impossible to do therapy with.
They believe they are always right, and are not willing to change their behaviors. And they do not. They only way to get them to change is to have an angle that suggests to them it is in their interest to change. I do not do couples therapy, so some other member of this panel may be a better person to ask about issues. Positive transference is necessary if you hope to have any therapy work.