The practical problem about charity (in one's prayer) is very hard work, isn't it? When you pray for Hitler and Stalin how do you actually teach yourself to make the prayer real? The two things that help me are (a) A continual grasp of the idea that one is only joining one's feeble little voice to the perpetual intercession of Christ who died for these very men. (b) A recollection, as firm as I can make it, of all one's own cruelty; which might have blossomed under different conditions into something terrible. You and I are not at bottom so different from these ghastly creatures.
Letter to Dom Bede Griffiths, 16 Apr 1940 intotheexpectation.blogspot.com