If our faith in the efficacy of Christ’s expiation for the sins of the believer is where it should be, there can be no room for shame. Shame in the believer can reveal a misunderstanding in the knowledge of the Lord Jesus’ full atonement, which is applied at rebirth.
It is completely understandable for the Christian in the outset to feel shame while the presence and workings of the “old man” are progressively realized, but continuing in the shame of it is the result of falling short in the comprehension of two vital elements; the regenerate one will continue to possess sin due to the sin source (old man); and the understanding that sinning (unintentionally) is expected, otherwise there is a prideful hindrance in the learning of God’s Word in the denying of these.
The heart and mind of the believer are to be joyous (as much as lies within us) “in the Lord” (Phil 4:4), which is impossible when beholding a guilt and sadness from sin. This will consistently hinder the thoughtfulness of all we are to be contemplating (v 8). Shame and remorse are rightfully expected during the initial revelation of our sinfulness, but as we (those born again) progress in the paces of the Spirit’s teaching of His Word, we are to eventually understand that God’s forgiveness completely clears one of guilt and shame, for His way is that we are not to be in sin (Rom 8:9)—though sin be in us.
An incomplete (but not absence) understanding concerning God’s forgiveness in Christ presents a veil against a heart of assurance, for if there be forgiveness what place has shame? Where should there be shame when sin (again, unintentional) is foreknown and expected? Otherwise it would be the same as God saying to the believer, “Shame on you for your sin?” Is it to humble one's self in retaining shame for the guilt of sin, which would present an incomplete propitiation; or is it to accept Christ's propitiatory work for a life which has been cleared of the guilt of sin—thus also of its shame?
Shame is for the unsaved, and also for the saved who've yet to understand there is no need for it in salvation. This can result in a "false humility" (2 Cor 2:18), which is usually in conjunction with the law-concept, in that it denies the sufficiency of the Cross-work of Christ by accepting that there must be an additional element beyond His sacrifice to effect the redemption of man!