The most basic way to work in the fourth stage of the meditation practice is to call the difficult person to mind, and repeat “May you be well, may you be happy, may you be free from suffering.” It’s good to imagine the difficult person smiling and happy.
You can also use your imagination in other ways. You can take the difficult person on any guided fantasy that you have been using in earlier stages (go back and re-read Methods of Cultivating Metta if you need to refresh your memory).
You can also imagine that it’s years from now, and that the two of you have resolved your difficulties and have now become good friends (it doesn’t just happen in romantic novels). In doing this you can “trick” yourself into feeling a sense of friendship for that person. It’s surprising sometimes how easily the mind can be tricked into suspending the judgments about others that we habitually make.
You can reflect on any good qualities the difficult person might have. Often we selectively “filter out” any good qualities from our perceptions, a bit like the kind of journalist who doesn’t let the facts get in the way of a good story. Dwell on the positive qualities of the difficult person. Remember that other people no doubt see admirable qualities in this person — qualities, perhaps, that you do not allow yourself to register.
You can think about what you and this person have in common. Both of you want to be happy and to be free from suffering. Wouldn’t life be better for both of you if you were in greater harmony?
Often we experience resistance to cultivating lovingkindness for a person we have difficulty with. We think that that person being happy would be a kind of “reward” that we’d be giving them — a reward that they don’t “deserve” because we dislike this person and therefore they can’t possibly deserve to be happy. (How peculiarly egocentric we are, that we believe other people’s happiness should conform to our own degree of liking and disliking for them). But you can consider that actually we’re doing this for ourselves — anger and ill will are painful states, and if we can let go of them by wishing another person well then we become happier. As a famous Buddhist teaching reminds us, it is anger and hatred that is our real enemy.
Another approach is to consider that if you had the history of the person you dislike, if your experiences were his or her experiences, if your conditioning was the same as his or hers, then your actions would be his or her actions. Or as the French saying goes, “Tout comprendre, c’est tout pardonner,” or “To know all is to forgive all.”
Lastly, the Dalai Lama is fond of quoting Shantideva, where the 7th Century master reminds us that without enemies we have fewer opportunities to practice patience, and since patience is a virtue we should therefore be grateful to our enemies for giving us this precious opportunity: “since my adversary assists me in my Bodhisattva way of life, I should long for him like a treasure.”