Mourn!!!

Then David said to Joab and to all the people who were with him, “Tear your clothes and put on sackcloth and mourn before Abner.” And King David followed the bier. They buried Abner at Hebron. And the king lifted up his voice and wept at the grave of Abner, and all the people wept. And the king lamented for Abner, saying,
“Should Abner die as a fool dies?
Your hands were not bound;
your feet were not fettered;
as one falls before the wicked
you have fallen.”
And all the people wept again over him. Then all the people came to persuade David to eat bread while it was yet day. But David swore, saying, “God do so to me and more also, if I taste bread or anything else till the sun goes down!” And all the people took notice of it, and it pleased them, as everything that the king did pleased all the people. So all the people and all Israel understood that day that it had not been the king's will to put to death Abner the son of Ner. And the king said to his servants, “Do you not know that a prince and a great man has fallen this day in Israel? And I was gentle today, though anointed king. These men, the sons of Zeruiah, are more severe than I. The LORD repay the evildoer according to his wickedness!”
(2 Samuel 3:31-39 ESV)
David was a guy on his way to the top.  He was destined to become king and he knew it.  But he did not allow that to harden his heart and trample people on the way.  Those around him didn't always get that.  They began to "take people out" without a thought or feeling of sorrow or regret, claiming to be doing it "for David."  In this world it is easy for us to become hardened towards the value of each and every life - to see others as in our way or to be stepped on, and cast aside when they are no longer useful to us.  We need to be able to grieve, and to do so sincerely and righteously.  David both demonstrated it and demanded it. I'm sure that everyone wasn't "feelin' it", but he wanted them to know they should. How hardened are you?