Paul, remarking on the utter futility of salvation and healing through law remarks:
I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree that the law is good. So then it is no longer I that do it, but sin which dwells within me. For I know that nothing good dwells within me, that is, in my flesh. I can will what is right, but I cannot do it. For I do not do the good I want, but the evil I do not want is what I do. Now if I do what I do not want, it is no longer I that do it, but sin which dwells within me.
So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inmost self, ¶ but I see in my members another law at war with the law of my mind and making me captive to the law of sin which dwells in my members. Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord! So then, I of myself serve the law of God with my mind, but with my flesh I serve the law of sin. (Ro 7:15–25).
In a similar vein, he tells the Colossians that ethelothreskia (which the King James translators aptly render as “will-worship”) is a waste of time. What we require (and God freely gives) is grace and mercy for our frailty, not gritted teeth and demands to do the impossible. Bob Newhart provides comic commentary on that reality here: