According to the text, what is one of the reasons accurate self-knowledge is a hallmark of mental health:

Accurate self-knowledge seems to be a hallmark of mental health. ... Your ideal self is your view of what you could do and your ought self is your view of what you should do. According to the theory of self-esteem, low self-esteem might serve as a warning signal for rejection. Sociometer.

Well, l think that some effective communication is, emotional barriers and lack of attention, interest distraction or irrelevance. also some physical disabilities such as hearing problems or speech difficulties.      l hope i am correct  and you good luck.