Can you imagine if we acted on every emotion we felt ? we would all be serial killers, we would have robbed banks, and slept with thousands of people of the opposite sex some people the SAME SEX. In other words we all go through life restraining and disciplining our lives around a set of values.

In the believers case our values come from the Word of God and especially the teachings of Christ. So the bible sys be angry but sin not. Its not a sin to be angry but it could become sin to act on it. So we learn to speak the truth in love and come to agreement with our adversaries whilst we are in the way.

Hope this helps sorry