I think I just found the answer to why David was a man after God’s own heart.

Here it is.
Are you ready?
Two words: Conviction and Repentance
Not just any conviction and repentance.
IMMEDIATE conviction and repentance.
Remember when God told David to not harm Saul … you know don’t touch the Lord’s anointed, despite the fact that Saul was just trying to kill him. Then, David cuts off a portion of his garment.
I’m thinking … “Big deal. He didn’t harm Saul (the Lord’s anointed). He just cut off a little piece of material. No harm done. Right? I mean the man is trying to kill him.”
Wrong.
It didn’t matter what Saul was doing.
It’s all about the heart. 
It’s about God’s Word being God’s Word no matter what the circumstance (even when someone is trying to kill you and whether you think it’s fair or not).
David’s heart was malicious at that moment. Angry. Ready to harm and hurt.
Even though it was such a minor thing, David realized it was a major heart thing.
David then immediately repents and even apologizes to his men for doing this.
Why is it so hard for us to recognize the conviction and go to God right at that moment? Then do something about it? Put action behind our words?
This quote by Beth Moore pretty much sums it up:
“One sure measurement of our proximity to God, whether near or far, is the length of time between conviction and repentance.”
Why do I wait?
I want to know my sin immediately and change my ways immediately … not drag out the whole process for weeks, months, years.