Therefore David took hold of his own clothes and tore them, and so did all the men who were with him. And they mourned and wept and fasted until evening for Saul and for Jonathan his son, for the people of the Lord and for the house of Israel, because they had fallen by the sword. II Samuel 1:11-12
Today death is so trivial because people are watching it every day on television or reading about it in the news. Experiencing losses comes in many forms: death, moving away, broken relationships, loss of a job or health, etc. A defense mechanisms that many people use in handling loss is to minimize its significance. We convince ourselves that the loss is not a big deal or get into some busyness to forget.
Others are going to hurt us intentionally or unintentionally and we will do the same to them. It is so difficult to not dwell on the pain that causes us emotionally and physically. David was able to grieve not just for his best friend, Jonathan, but for Saul who had been trying to kill him for years. David refused to get stuck in the past hurts that Saul had caused him.