"A man after God's own heart" is what David is called in I Samuel 13:14. So, it is very helpful to discover that he is not sinless but a man of great passions and driven by great desires.
He has a violent temper and is a vicious, cruel killer. However, when the Lord puts the finger on him, he is also completely repentant. He has the whole spectrum of emotions that you and I have, yet God calls him a "man after His own heart," because, even though he fails God many times, he loves God wholeheartedly.
God Chooses David to be King- King Saul, though a talented king, had stopped obeying God early in his career, and had begun turning selfish and evil. So God told the prophet Samuel he would remove Saul from being king, and replace him with "a man after his own heart".
The Battle with Goliath- David approached Goliath on the run, sling in hand. His first shot penetrated the giant's forehead, and he fell facedown, dead.
Saul Turns on David- Saul threw his spear, and David narrowly dodged the spear. Fearing for his life, David finally decides he isn't safe and left town that night.
David in Exile- David wandered the wilderness, living in caves. Many other fugitives sought him out, and soon he had a community of 400 families in his care.
David Spares King Saul- David passed up a chanced to kill Saul, out of respect for the LORD, and he displayed the hem of Saul's robe as evidence. He furthermore promised he would never harm the king the LORD had chosen.
King Saul Dies in Battle- Saul was mortally wounded, and fearing that his enemies would capture and torture him, he takes his own life.
David, King of...