My wife pointed this out to me recently:
James 4:4-5 4 You adulterous people! Do you not know that friendship with the world is enmity with God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God. 5 Or do you suppose it is to no purpose that the Scripture says, "He yearns jealously over the spirit that he has made to dwell in us"?
James is pretty strong when he calls some of his church members - enemies of God - i.e. those who wish to murder God
it is no wonder that some of the church fathers called sin - Deicidium - or God-murder
sin seeks to ungod-God
yet - the sin is not defined so much by our rebellion/transgression or disobedience - but much more - "by His jealous Spirit"
It is the strength of the love of God that makes sin so serious
if you had a lousy relationship with your wife, then she couldn't care less if you flirted around with another
but if your wife loved you with a jealous and passionate love, then every little tiny glance of another is tantamount to the adultery - every thought (as Jesus says) - is equivalent to sleeping with another
therefore He yearns jealously over us, and yet is constantly able to wipe the slate clean, time after time though we constantly stab Him in His heart..
It is no wonder then the Spirit so constantly grieves ..
and when we flee the youthful passions (think Ruth & Boaz) - He is prepared to use us so mightily