You can put a knife in a man and then draw it out. It won't matter how many times you say I'm sorry, the wound is still there. Our Lord told us to be angry, but sin not . Just take one step over that spiritual boundary line and the results become the handiwork f Lucifer. He is so full of anger and frustration that he gladly and repeatedly prods us to the edge.
Self justification is our way of saying it is someone else's fault.
Wit his brother's blood still on his hands, Cain saw the problem as Abel's smug spirituality. King Saul blamed David, then Jonathan, and finally, God - but never himself. David, while venting his anger on the slayer of a poor man's lamb, couldn't see his own sin.