from Mindfulness in Plain English
For all practical purposes, if all of your enemies are well, happy and peaceful, they would not be your enemies. If they are free from problems, pain, suffering, affliction, neurosis, psychosis, paranoia, fear, tension, anxiety, etc., they would not be your enemies. Your practical solution to your enemies is to help them to overcome their problems, so you can live in peace and happiness. In fact, if you can, you should fill the minds of all your enemies with loving-kindness and make all of them realize the true meaning of peace, so you can live in peace and happiness. The more they are in neurosis, psychosis, fear, tension, anxiety, etc., the more trouble, pain and suffering they can bring to the world. If you could convert a vicious and wicked person into a holy and saintly individual, you would perform a miracle. Let us cultivate adequate wisdom and loving- kindness within ourselves to convert evil minds to saintly minds.
When you hate somebody you think, "Let him be ugly. Let him lie in pain. Let him have no prosperity. Let him not be right. Let him not be famous. Let him have no friends Let him, after death, reappear in an unhappy state of depravation in a bad destination in perdition." However, what actually happens is that your own body generates such harmful chemistry that you experience pain, increased heart beat, tension, change of facial expression, loss of appetite for food, deprivation of sleep and appear very unpleasant to others. You go through the same things you wish for your enemy. Also you cannot see the truth as it is. Your mind is like boiling water. Or you are like a patient suffering from jaundice to whom any delicious food tastes bland. Similarly, you cannot appreciate somebody's appearance, achievement, success, etc. As long as this condition exists, you cannot meditate well.