Mostly, the difficult person exhibits behaviors that resemble that of a needy, demanding child. When she fails to get what she wants, she slips into a victimized complaining mentality. She thinks she deserves and must be given special treatment.
Psychologically, abrasiveness is a defense mechanism or mask of the difficult person against closeness or fear of being injured again. Unconsciously, he or she recreates in the present the early abusive relationship he or she experienced n the past.
So when you're dealing with a difficult person, understand that his or her behavior is not a personal attack on you. He or she simply is "tortured," damaged psychologically by life trauma experiences. He or she needs special therapy and care. To be treated empathically and wisely rather than hatefully or fearfully.