The modern notion of "forgiving ourselves" actually stems from an incomplete and inadequate Biblical understanding of God's forgiveness. That is, if we fully experience His pardon for our sins, we will find no need for our own personal absolution and cleansing of our conscience.
"Having a High Priest over the house of God; let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience" (Hebrews 20-22).
Only our great High Priest, the Lord Jesus Christ, can birth and maintain in us "a true heart in full assurance of faith," and only He can cleanse us from "an evil conscience." In times of sin against God and others, the Holy Spirit works in believers to expose our errors, to lead us to remembrance of our Savior's intercessory sacrifice on our behalf, and to elicit honest contrition for our unbelief and disobedience. When we respond in genuine faith and repentance, the Spirit magnifies the salvation of the Lord Jesus in our hearts and minds to the degree that we go forward in peace and renewed devotion to God and others (which may at times involve Spirit-led confession, apology, and restitution to those against whom we have sinned). "Where sin abounded, grace did much more abound, that as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life by Jesus Christ our Lord" (Romans 5:20-21).
Believers who walk in ongoing and paralyzing remorse about sin fail to adequately understand the efficacy of Christ's work on our behalf. Thus, the notion has arisen, even among Christians, that we must "forgive ourselves." No Biblical basis exists for such an erroneous concept. Our need is rather to "grow in grace, and in the knowledge of our Lord and Savior Jesus Christ" (II Peter 3:18). "What is it about my Lord and His redeeming work on my behalf that I do not know well enough in order to walk in the peace of a cleansed conscience?" This is the question the remorse-plagued and paralyzed believer must ask if he is to have any hope of the tranquil heart our Lord desires His children to experience. God's answer will exalt the Savior, emphasize His once for all sacrifice, enlarge understanding of His ongoing intercession, and enable the trusting and repentant believer to go forth from the altar of mercy in the peace for which the Lord Jesus suffered so much to provide. Forgive ourselves? Not when the Holy Spirit applies the power of our Savior's sacrifice and intercession to needy hearts.
"This man, after He had offered one sacrifice for sins forever, sat down on the right hand of God."
"There is forgiveness with Thee."
"How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?"
"He is able also to save them to the uttermost that come unto God by Him, seeing He ever liveth to make intercession for them."