“As for me, I said, “O Lord, be gracious to me; heal me, for I have sinned against you!”” -Psalm 41:4
“As for me,” is translated from the pronoun,אֲֽנִי־ (ani), and is used for emphasis. The Psalmist is emphasizing personal responsibility in the situation at hand—much like Joshua did when he covenanted before Israel to the serve the Lord instead of the other gods.
“And if it is evil in your eyes to serve the Lord, choose this day whom you will serve, whether the gods your fathers served in the region beyond the River, or the gods of the Amorites in whose land you dwell. But as for me and my house, we will serve the Lord.”” -Joshua 24:15
The Psalmist is not blaming his malady on God or on nature, or on fortune or fate. He alone is responsible for sinning against God, and thus rightly incurred God’s chastising hand (Hebrews 125ff) Having confessed his sin, he also petitions for grace—God’s undeserved favor. This request is made on the basis of God’s objective nature, not his own merit.
God is not only immensely just; he is, at the same time, immensely gracious. The same consistent nature possessed by God that issued his malady for sinning will also extend grace for confessing.