Nothing new here: managing involves handling some difficult relationships. Communicating effectively and balancing between reaching the other person and staying in your power is key. Often, difficult relationships have less to do with the content of a situation and more to do with personalities and emotions. Your communication strategy then, must reflect this.
Identify now a difficult relationship you have at work. What is your communication strategy with this person? It would behoove you to look beyond the work related aspects of the relationship (their position in the organization relative to yours, their responsibilities in your organization) to personal and emotional aspects of the relationship (the emotions they show at work that make the relationship difficult, the emotions you have about them, how you react to your interactions with them, the differences and similarities of your personalities). Get a fuller picture of what you are dealing with.
Once you have that picture, let your communication strategy reflect it, at the same time maintaining your own integrity and power in the relationship.