If you don’t believe me when I say King David was a royal jerk, you need to read this psalm for yourself. His paranoia is in full bloom, as he wishes every bad thing imaginable on his enemies.
“Let his days be few,” David orders YHWH, “And let another take his office. / Let his children be fatherless, / And his wife a widow.” It gets worse. He even wants the man’s children annihilated.
As for himself — the poor, poor, pitiful king — David says, “But You, O God the Lord, / Deal with me for Your name’s sake; / Because Your mercy is good, deliver me.” Lord, have mercy is right.