The first line of "Yawara" seemed familiar--Katsu to omou na, omoeba make yo- -, so I consulted Ivan Morris' The Nobility of Failure: Tragic Heroes in the History of Japan---the last chapter in the book about the WW II Kamikaze pilots.
Sure enough, there again was the first line of the song: Never think of winning! Thoughts of victory will only bring defeat... from a popular song of the kamikaze.