D A V I D & S A U L
Both Saul and David were anointed by God as the kings of Israel, both of them conquered several battles, and both of them committed sins. But the difference is that, Saul was more concerned about his personal ego than his personal relationship with God while David was primarily concerned about his relationship with God than his personal ego.

King Saul regarded the respect of people mostly, but King David regarded his reconciliation with God more than anything else. When King Saul committed a sin and God sent Prophet Samuel to rebuke him, king Saul realized he had sin but he was not ready to let go of his ego. "Then he (Saul) said, “I have sinned; yet honor me now, please, before the elders of my people and before Israel, and return with me, that I may worship the Lord your God.” 1 Samuel 15:30. But when David sinned and God sent Prophet Nathan to rebuke him, he humbled himself before God and man, and so he was pardoned. "So David said to Nathan, “I have sinned against the Lord.” 2 Samuel 12:13.

Some people do say that David committed sins but God forgave him because he knew how to praise God very well. That is a serious error and un-biblical conclusion. Such conclusion can mislead people, and it's misleading many people. Sacrifice of praise to God cannot cover your sins, in fact David himself said that any sacrifice in sin is useless to God.

"For You do not desire sacrifice, or else I would give it;
You do not delight in burnt offering.
The sacrifices of God are a broken spirit,
A broken and a contrite heart—
These, O God, You will not despise......Then You shall be pleased with the sacrifices of righteousness,
With burnt offering and whole burnt offering;
Then they shall offer bulls on Your altar." Psalm 51:16, 17, 19.

David received the mercies of God because he confessed and forsook his sins. Saul confessed his sin of wickedness at different times when he was pursuing David, but he did not stop pursuing David. But David confessed his sin of adultery and murder, and he never continued in the sins again. Have you read it anywhere in the Bible that David committed adultery after he had confessed to God? Never! Praise and worship does not cover sin as many preachers are saying today, thanksgiving and sacrificial givings cannot get you the mercies of God as many modern preachers are claiming today. The only two things that guarantee God's mercies are confession of sin and forsaking the sin, that is, to discontinue in the sin. Proverbs 28:13, "He who covers his sins will not prosper, But whoever confesses and forsakes them will have mercy."

Do you need the mercy of God like David? Do you want to be a precious child of God, a peculiar servant of God as David was? All you need is to humble yourself, open up, confess and discontinue in such sin.