“Then you will remember your evil ways, and your doings that were not good, and you will loathe yourselves in your own sight for your iniquities and your abominations. Not for your sakes do I do this,” says the Lord Yahweh, “be it known to you. Be ashamed and confounded for your ways, O house of Israel.”
That there were such periods of repentance after the exile we need not doubt (e.g. Ezra 10:1; Nehemiah 9). By the destruction of Jerusalem and the exile a deep lesson was learned by Israel, especially the true Israel. So His true people mourned over their past sins, and loathed themselves for what they had been. They really were ashamed and confounded to think of what had been. The same should be true for true Christians today. They rejoice in their forgiveness, but they loathe what they were and wonder how they could ever have been like it.