[reasonisfaith]

It’s all one classification: sinning. But the Lord speaks to us about where sin begins, in the heart. As your post shows and many other verses of God’s word.

[HarleyD]

Sin is sin. As Christians make too light of it in my opinion (including myself). If there was "free will" personally that would be wonderful for then I could choose not to sin ever again. But that isn't the case. Though we're Christians we fail and sin. Like David, we learn from our sinful behavior although it might cause us problems. It is like Paul stated:

Rom 7:19 For I do not do the good I want, but the evil I do not want is what I keep on doing.
Rom 7:20 Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.
Rom 7:21 So I find it to be a law that when I want to do right, evil lies close at hand.
Rom 7:22 For I delight in the law of God, in my inner being,
Rom 7:23 but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members.
Rom 7:24 Wretched man that I am! Who will deliver me from this body of death?
Rom 7:25 Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin.