Directing lovingkindness, or sending goodwill, toward people we feel very good about is usually easy to do. Directing goodwill to your grudge-list people is hard to do. What makes it possible is recalling at least one positive thing about each person on the list, the remembrance of which opens your heart. The key is forgiveness. To do anything less is painful.
— Sylvia Boorstein, It's Easier Than You Think