It is by far more of a challenge to empathize with your enemy. By developing compassion towards those you normally wouldn’t think twice about is the only way to develop deep compassion for all sentient beings. If you view those who have behaved horribly towards you as beings who are giving you ample opportunity to practice compassion and patience, you will find you have no enemies but many teachers.
If you are looking for ways to help cultivate compassion in yourself, try volunteering at a local animal shelter. If the shelter is one that must put animals to sleep then you can show compassion for the animals by playing with them and making their last days joyful. It is very sad to be around animals that are going to be put to sleep and not being able to save them. Since it is impossible to save them all, the least you can do is take the dogs for a walk, play with the cats and let them know kindness. Hospice is another way to show compassion. Providing companionship to help enrich another person’s life is a rewarding experience that will test ones limits. Not everyone can work with people and animals that will be dying. Some of those who do have embodied the essence of compassion to the extent many of us are still aspiring to.
Another way to cultivate compassion is to change how you perceive people and situations. Take for example those nice people working as a telemarketer. Instead of thinking of them as annoying persons who live to disrupt your evenings think of them as beings that are sacrificing their evenings in an attempt to scratch out a living. Many of them have families to support and are doing the best that they can at a job that people seem to despise. Instead of leading them on by teasing them or just simply hanging up on them, be positive and say a firm and kind good bye then hang up.