There is a natural dynamic tension between the needs and preferences of the individual and the needs and preferences of those with whom we relate, especially close relationships. Maintaining a strong sense of self in this context may produce conflict. How we handle that is the key to success and balance and one measurement is "differentiated vs undifferentiated".
While going through some old files I found an article I had saved on that topic from the September 1988 issue of Atlantic Monthly written by Michael Kerr. A rather long and analytical piece, here are some brief excerpts, some paraphrased.
To navigate through the quagmire (of relationship conflicts) requires a well thought out direction and a tolerance for intense feelings. Is the effort based mainly on "emotional reactivity to others (undifferentiated) or thoughtfully determined direction and goals for oneself (differentiated)? Differentiation is a product of a way of thinking that translates into a way of being. Trying to achieve a higher level of "D" and a more solid self means increasing one's capacity for emotional detachment or neutrality. And that depends on changes in one's thinking.
One must have confidence in an alternative (less reactive) way of thinking and being that one's feeling responses do not automatically dictate one's actions. Might be called 'thinking it through".
Such changes are reflected in the ability to be in emotional contact with a difficult, emotionally charged problem and not feel compelled to preach about what others should do, not rush in to fix the problem, and not pretend to be detached artificially. The classic "fight or flight" primitive options that stressful events can create.The lower one's "D" the less adaptive he/she may be to managing stress, and the more likely one is to be anxious and plagued by negative thoughts. And specifically, in poor levels of "D", the negative thoughts tend to take on more personal, permanent (no end in sight), and generalized (affects everything) qualities.
So, it has been shown that when people can maintain "comfortable contact" with emotionally significant others they are more likely to adapt more successfully to stressful events and handle them more "specifically" and "objectively".
Finally, it is possible for one to have such a history of either personally being in, or in a family of, highly reactive relationships that it becomes the "norm", is sought out, and a lack of emotionality can be experiences with boredom or distrust (this is not real, it will not last).