If we could read the secret history of our enemies, we should find in each man’s life sorrow and suffering enough to disarm all hostility.

Henry Wadsworth Longfellow (1807-1882) American poet
“Table Talk,” Drift-Wood (1857)
    (Source)

More discussion of this quotation here: If We Could Read the Secret History of Our Enemies, We Should Find in Each Man’s Life Sorrow and Suffering Enough To Disarm All Hostility – Quote Investigator.