My shield is God Most High, who saves the upright in heart

Psalm 7:1-17 

Lord my God, I take refuge in you; save and deliver me from all who pursue me.

Lord my God, if I have done this and there is guilt on my hands— if I have repaid my ally with evil or without cause have robbed my foe— then let my enemy pursue and overtake me; let him trample my life to the ground and make me sleep in the dust. 

Let the assembled peoples gather around you, while you sit enthroned over them on high.  Let the Lord judge the peoples. Vindicate me, Lord, according to my righteousness, according to my integrity, O Most High. Bring to an end the violence of the wicked and make the righteous secure— you, the righteous God who probes minds and hearts.

My shield is God Most High, who saves the upright in heart. God is a righteous judge, a God who displays his wrath every day.

Whoever is pregnant with evil conceives trouble and gives birth to disillusionment. Whoever digs a hole and scoops it out falls into the pit they have made.

I will give thanks to the Lord because of his righteousness;  I will sing the praises of the name of the Lord Most High.

Why?
David fully depended on the Lord, David prayed to the Lord to save him from enemies.

David always followed the words of the Lord, if he did something wrong may the Lord judge him.

How?

So am I will give thanks to the Lord and sing the praises of the name of the Lord Most High.