Do you know why David was a man after God’s own heart? Listen to David speak, and you will see where he put his trust, and you will see the awesome confidence it gave him, but not in himself rather it was in God,

When I cry out to You,
Then my enemies will turn back;
This I know, because God is for me.
In God (I will praise His word),
In the Lord (I will praise His word),
In God I have put my trust;
I will not be afraid.
What can man do to me?
(Psalm 56:9–11)

David’s talk of trust in God and praise of His word, was not just talk, but he lived it, and he had seen in his life that when he cried to God, the enemies turned back, because God was for a man like David.