I was given a book sometime back entitled, "Our Oneness with Christ - A Study in Living by Grace Through Faith" written by David Kuykendall. Allow me to share some direct quotes concerning our sin addiction.
"The New Testament uses three terms to describe our sin problem: 'sin,' 'old man' and 'flesh.' The Old Testament, in the second and third chapters of Genesis, uses yet a fourth term, 'the knowledge of good and evil.'" (p29)
"These verses (Genesis 3) show conclusively that it was 'the knowledge of good and evil' with which Adam infected himself--and us. Notice especially the reason Adam and Eve were sent from the garden. They were now as God, 'to know good and evil' (Genesis 3:22)." (p30)
"Just as surely as we have two eyes and ten fingers because we are in the race of Adam, we have an attitude of omniscience for the same reason. Take heed! Our know-it-all attitude is not content to function quietly and only for the individual in whom it abides. It roams far and wide. It knows no limitations. It moves in all directions, whether horizontal or vertical. It passes judgment on and makes decisions for anybody and everybody--even the Lord God. For example, more than one serious problem of fellowship has developed in one of the Lord's churches because one or more members insisted that their point of view was the correct one. Most everyone who has been involved in the Lord's work for only a few years has experienced the grief and strife among the people of the Lord that the know-it-all attitude has created." (p32)
"What, then, is our flesh? Our flesh is our know-it-all attitude, which is the deepest form of self-confidence. When we live 'in the flesh,' we trust ourselves." (p33)