1 Samuel 23:6-29
To the point of ruthless delirium, Saul was infatuated with power and status. It caused him to disregard God, neglect his responsibilities and harm the people he cared about. We have as much to learn from him as we do from David. Similar to David, Saul came from humble beginnings and was an unlikely choice for king. But he lacked a heart for God and thus got swept up by the world.
In Matthew 16:25, Jesus stated: For whosoever will save his life shall lose it: and whosoever will lose his life for my sake shall find it. For what is a man profited, if he shall gain the whole world, and lose his own soul? or what shall a man give in exchange for his soul?
Saul never lost his life for God. He gained, gained, gained but never dedicated any of it, and certainly not his soul, to God or His purposes. Our individual agenda should always be secondary, (or even better: altogether irrelevant,) to God's plan.
The notable difference between Saul and David: David dedicated himself to be a servant of God's will; Saul dedicated himself to his own will, and thereby enslaved himself to his desires. Had he relied on and learned from God, Saul would have been able to overcome the selfishness, hostility, jealousy, ego and all other character flaws and corrupt tendencies and bad inclinations that he had.
David loved and was obedient to the Lord and the Lord protected David; despite Saul's dogged efforts to kill him, David continually escaped. And David's continual dependence on God allowed him to cling to the best of himself. He was able to overcome the emotions he, reasonably, could have felt: anger, despair, retaliatory.
The same was true for David's best friend, Saul's son, Jonathan. According to tradition, Jonathan was supposed to be king after Saul. Instead, God chose David. Jonathan loved the Lord and chose to celebrate David as God's chosen. Jonathan loved his best friend and God more than status, power or tradition of the world. He trusted God to distribute justice, to alter his life to accommodate His plan, even if it meant he would never have the power or status he grew up thinking would be his.
Saul pursued David through the wildernesses of Ziph and Maon and onto a mountain. Saul and his men were one side, David and his on the other. Saul's men surrounded David; he was trapped. Then suddenly came a messenger to Saul: the Philistines had rerouted to continue their attack on the city David had just defended. Saul had to abandon David, disassemble his trap of men, and turn to fight the Philistines. Once again, God provided David escape.