In the first reading, David spares the life of King Saul who was hellbent on killing him. Saul acknowledges that David is a better man and will become king someday. Then he stops hunting David and returns to his palace.
How many of us have had this experience of being maltreated but instead of taking revenge, we forgave our enemies? For sure we all have people who don't like us, are jealous of us or cannot stand us. Yet do we have Christian love to forgive them? Do we want to forgive them? And in the first place, why should we forgive them? The answer is -- because Jesus had first forgiven our sins. Jesus has erased the memory of our wrongdoings and has given us the grace of repentance and a change of life.
Some of our enemies will never change, but if we see them as people whom God has also forgiven, then who are we not to do so ourselves?