From Lust to Murder

2 Sam 11:27b But the thing David had done displeased the Lord.

2 Sam 11 reveals the story of Davids multitude of sins with Bathsheba.  First, he didn't lead his army into battle.  I'm not sure this is a sin in the Lord's eyes, that is a difficult one to discern for me, but it was the clearly stated that it was the "time that kings go off to war" and the worldly expectation was that the king led his army into battle.  Instead, David stayed home.  Late in the evening he was on his roof and saw Bathsheba bathing.  Upon inquiry, he found out her name as well as her marital status.  I'm curious as to what went through his mind when he heard the words "she is Bathsheba, the wife of Uriah the Hittite."  Why did he continue beyond lust when he discovered she was married?  He had to know that he had already sinned and to "invite" her into his palace was to cause her to sin as well (note that David was already married and had numerous wives and concubines).  When she became pregnant as a result of this adulterous affair, he called Uriah home from the war to provide a cover for her pregnancy.  This had to have happened over a period of a few months, so this isn't some short-term loss of self-control.  This is a long-term carefully thought through scheme.  When Uriah refused to avail himself the luxury of being home, David had him killed in a useless mini attack on a besieged city that also cost the lives of others.  Lust, covetousness, lies, murder, and illegitimate pregnancy and THIS is a man after God's own heart?  Wow!
So, why did it take Nathan's confrontation in the next chapter to finally get through David's thick skull the depth of his depravity?  Sin is insidious and Satan is incredibly and completely deceptive.  We rationalize, make excuses, and then compare ourselves to others to avoid the confrontation each and every one of us needs.  Why?  Why do we get so deep into sin?  How do we become so incredibly blind to its effects on us and perhaps more importantly why do we not see the effects on others?  Why do we sin anyway when others are so terribly affected?  Even a man after God's own heart was not immune to the overwhelming attack of Satan.  If David could be so blind to his own depravity, what have I done?