I have sinned — i.e., “Putting the case that I have sinned, yet what then can I do unto Thee, O thou keeper of men? “with a possible allusion to Job 7:12, though the verb is not the same.
O thou preserver of men. — “Why hast Thou set me as a mark for Thee to expend all Thine arrows upon?” or, “Why hast Thou made me to be Thy stumbling-block, so that Thou ever comest into collision against me, so that I am become a burden to myself?”