Do we need to forbid the use of the term wretched as a valid descriptor of the sinner/saint? Though some may think so, I hope not. Does its use mislead and draw the elect away from the truth of who they are in Christ? I think not. The term seems, at times, to be an apt biblical description of the Christian's very real anguish regarding how far he is from actual righteous living. The word, as used by the apostle Paul in the last half of Romans 7, is more of a reflection on the plight of the continual struggle against our own sinfulness in light of God's saving grace than some downer-definition of our being.
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. 24 Wretched man that I am! Who will deliver me from this body of death?
Though fallen, we are creatures made in the image of God. Even more, as Christians we are children of God and joint heirs with Christ. Yet it is the very glorious gift of having been made new creatures in Christ (forgiven, adopted of God with new hearts) coupled with the continuing reality of sin within, i.e. we too often still choose to sin, which leads one to cry, "O wretched man that I am..." And yet thankfully, more than just that phrase comes into view from God's word. One finds the triumphant answer of good news which follows in Rom 8: 1 - There is therefore now no condemnation for those who are in Christ Jesus! Though still a sinner, the Christian can take it to the bank that one who is in Christ Jesus stands fully Justified (no condemnation) before God for Christ's sake apart from any works now and forever. Or as Paul puts the same truth in another epistle, a sinner is fully saved by grace through faith, and that not of himself (Eph. 2:8-9). It is this transforming and sanctifying Gospel that Paul calls "the power of God for salvation to everyone who believes" (Rom. 1:16).
I sometimes think that as modern Christians we have become unconsciously affected by the self-esteem movement of the last 40 years and thus shrink back from certain blunt biblical language which is used to describe God's people in light of their fallen state (see Is. 41:14). We seem to want to minimize and sanitize our sinful natures, put on blinders, and adopt what is basically a heavenly-transformed-only-view regarding our status as children of God. I'm forgiven! I'm a new creature in Christ! Don't confuse things by bringing up the present reality of my sin... But though saved, we nonetheless are still actively fallen sinners. We are Christians who all too often choose to sin real sins. Regarding this Ursinus writes in his Heidelberg Commentary:
The reasons, on account of which the will in this third degree chooses and does in part both the good and the evil, are the following: 1. Because the mind and will of those who are regenerated, are not fully perfectly renewed in this life. There are many remains of depravity which cleave to the best of men, as long as they continue in the flesh, so that the works which they perform are imperfect, and defiled with sin. “I know that in me, (that is, in my flesh,) dwelleth no good thing.” (Rom. 7:18) 2. Because those who are regenerated are not always governed by the Holy Spirit; but are sometimes forsaken of God for a season, that he may thus either try, or humble them. Yet, although they are thus left to themselves for a time, they do not finally perish, for God, in his own time and way, calls them to repentance. “Take not thy Holy Spirit from me.” “0 Lord, why hast thou made us to err from thy ways, and hardened our heart from thy fear. Return, for thy servant’s sake.” (Ps. 5 1:13, Isa. 63:17) In short, after regeneration, there is a proneness to choose partly the good, and partly the evil. There is a proneness to the good, because the mind and will being illuminated and changed, begin, in some measure, to be turned to the good, and to commence new obedience. There is a proneness to the evil, because the saints are only imperfectly renewed in this life—retain many infirmities and evil desires, on account of original sin, which still cleaves to them. Hence the good works which they perform are not perfectly good.
Therefore if “I know that in me, (that is, in my flesh,) dwelleth no good thing” (Rom. 7:18), then it is indeed fair to say "O wretched man that I am." And yet transcending that burden is the glorious truth of God's abundant grace in Christ Jesus, i.e. the salvation of the ungodly. Which causes us to confess with David (Rom. 4:6-8) that of Him we are truly blessed.