If you are the kind of person whose mood is easily affected by the words of others, then the enemy will provide plenty of opportunities for you to encounter people who say and do things that will offend you and/or kill your good mood.
The devil understands the twofold effect of a Christian with a stinky attitude. It kills that person's effective witness for Jesus and it might stop us from going and doing something God wanted to bless. The good news is God has given a solution. [Proverbs 19:11] A person's wisdom makes him slow to anger, and it is his glory to overlook an offense. We wouldn't have been told to overlook offenses unless that was a realistic expectation.