If you feel an increased level of emotions, stay calm but mention the fact. Ask: "It seems to me that you are frustrated. What's behind this?" Listen to the answer and ask further. Make sure you have correctly deduced the reasons for frustration.
In your own words, summarise what you have learned about the uncomfortable feelings of your subordinate and the causes. Then arrange a solution together.
-kk-
Article source Harvard Business Review - flagship magazine of Harvard Business School