Search the Bible for the phrase "forgive yourself" — it isn't there. Not in the Old Testament, not in the New. The concept as commonly taught — that you must grant yourself the same pardon you'd extend to someone else — has no direct Biblical basis. What the Bible speaks about instead is receiving forgiveness, being washed, being declared clean, having sins removed as far as the east is from the west.
This distinction matters practically, not just theologically. Self-forgiveness as a concept places you in the role of the judge who must decide whether your case is closed. You become both the offender and the one who absolves. The problem is that you are not the primary offended party — God is. And he has already spoken. The struggle is not that you haven't yet granted yourself forgiveness; the struggle is that you have not yet believed that you are already forgiven.
1 John 3:20 addresses this directly: "For if our heart condemn us, God is greater than our heart, and knoweth all things." John is saying: when your own conscience refuses to relent, when the internal judge won't acquit you — God's verdict is larger. His knowledge of what you did is complete. All of it. And his declaration of forgiveness, in Christ, stands over your internal tribunal. The verdict was rendered before your conscience started the trial.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.