Jamie, don’t think I said that Davis was regretful, just making an incredibly understated observation that one could file under “W” for “wisdom is dearly purchased.”
The source of this may be found on P.129 of Alf J. Mapp, Jr.’s 1963 book, “Frock Coats and Epaulets”: “In these days, he (Davis) wrote a two-volume apologia for that way (i.e., the Old South’s way of life), the Rise and Fall of the Confederate Government. Characteristically, he asserted in it that the war had proven secession impractible but had not proved it illegal…”