Be merciful to me, O God, for men hotly pursue me; all day long they press their attack.  My slanderers pursue me all day long;  many are attacking me in their pride.

Iv'e noticed (It's kinda hard to ignore) that David is usually in a little bit of trouble.  Apparently they are coming at him all day long, no hope for bit of peace for the day, and he always has to run and hide, so he doesn't die.

On no account let them escape; in your anger, O God, bring down the nations.

After always having to run away from the bad guys that are trying to KILL HIM!, I'd want them to be finished with too.