Romans 7:21-23
(21) So I find it to be a law that when I want to do right, evil lies close at hand. (22) For I delight in the law of God, in my inner being, (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.
Paul defines the conflict or battle that is constantly raging between our spiritual selves and our physical selves. When we accept Christ as our savior, we accept GOD's law as a basis to live our lives by. Our mind, heart and soul tells us what is right and wrong but our worldly beings are continuously tempting us to do the wrong thing. Sin dwells within us.
When we lie, we know it is wrong and that the consequences at best, lead to more lies and eventually facing the shame and embarrassment of being found out, yet we still do it. Paul states in Romans 7:14-15, (14) For we know that the law is spiritual, but I am of the flesh, sold under sin. (15) For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate.
This is all part of GOD's plan for us. We are made of sinful flesh but we possess a spirit. GOD wants us to resist the temptation of our flesh and strngthen our spirits so that when the time comes, we can be accepted to dwell with HIM who is pure spirit. GOD knows we will stumble and for that reason, HE sent HIS Son to save us from ourselves.