I think the most insidious things Christians do is gossip and hold grudges against one another. Really, what is gossip? It's nothing more than spreading your grudge against another to others. It's so easy to find myself in this trap.
So, that abrasive person at church said something that offended you. What do you do with that? Do you go home and lick your wounds and complain to a friend about how she offended you? Or do you act in mercy and consider that perhaps she has a weakness in this area and then pray for grace to be kind in spite of this? With many, the knee jerk reaction is to get bent out of shape and then tell someone how you were offended.
We don't have time for this nonsense. The judge stands at the door! Do I want to have to answer for why I disobeyed this direct command of God?