Rest in the LORD and wait patiently for Him; Do not fret because of him who prospers in his way, Because of the man who carries out wicked schemes. Cease from anger and forsake wrath; Do not fret; it leads only to evildoing. - Psalm 37:7-8 NASB
In the movie The Last Samurai an American soldier (Algren) gets captured by a band of Samurai after being hired to teach Japanese soldiers how to use western weapons. While he was in the Samurai camp he attempts to learn to fight with a sword. He is only moderately successful until one of his friends (Nobutada) explains his problem:
Nobutada: Please forgive, too many mind.Nathan Algren: Too many mind?Nobutada: Hai. Mind the sword, mind the people watch, mind the enemy, too many mind... [pause] No mind.
Notbutada's point was that by trying to pay attention to everything Algren wasn't effectively doing what he was meant to be doing. It is easy to have "too many mind", to focus on the events of the world, focus on those whom we see opposing the Lord, or even us personally. Our mind, however, is meant to be focused on the Lord. Trusting in Him. Our lack of trust in Him can lead to fear, worry and anger, none of which are productive.