David was a man after God's own heart. But why was David described this way? And what, exactly, does it mean?

Interestingly, David was only a child who had not accomplished anything king-worthy at the time Samuel prophesied about a man after God's own heart becoming King. But God knew David's heart and what he could do long before David had any idea what his future held. 

As we pursue friendship with God, our hearts have to take a particular posture.

Mrs. Joan Isoke.