The excellent interview with Father Zabelka reprinted on LRC today contains a program, whose first step is to love one's enemies. For those who wish to carry out that step, I highly recommend The Greatest Secret in the World. Mandino wrote it as a practical workbook for applying the principles laid out in his The Greatest Salesman in the World.
Mandino suggests, very simply, that one read a "scroll" of text 3 times daily (once of those aloud) every day for 5 weeks, and keep records on your behavior. Each scroll affirms important habits. The second scroll says, in part:
I will greet this day with love in my heart....
And how will I confront each whom I meet? In only one way. In silence and to myself I will address him and say I Love You. Though spoken in silence these words will shine in my eyes, unwrinkle my brow, bring a smile to my lips, and echo in my voice; and his heart will be opened.
This method, of improving virtue through reading affirmations aloud, is a time-honored tradition that works wonders. Most people read a book such as The Greatest Secret in the World and do not act on its simple instructions.
But, if you are in earnest to love others, I recommend getting a copy of either The Greatest Salesman in the World or The Greatest Secret in the World, and read scroll #2 to yourself 3 times a day for a month. Better yet, follow Mandino's whole plan of scrolls and recording your behavior.
