Forgiveness is primarily a matter of your mind and will. Love of neighbor is anchored in love of God. Therefore, it is possible to love the unfriendly neighbor on the level of the will. You must love your neighbor, be he friend or foe, because of God. It is not a matter of love of man for man, but you love your fellow man because Christ has commanded it. To forgive means to cease to harbor ill feeling because one has suffered at the hands of another. It is a simple reaction to feel dislike for a person hostile to you. This reaction in itself is not sinful, but is only a phase of the natural love of self. The feeling of hatred or aversion becomes sinful when you knowingly and voluntarily nurture and act upon it.
— Lawrence G. Lovasik, “Forgiveness,” Kindness.
Lawrence G. Lovasik (1913–1986) was a member of the Divine Word Missionaries (SVD) who wrote numerous books on the Catholic faith, with special attention to the importance of prayer and the Blessed Sacrament. His missionary work took him to the coal and steel regions of the United States. A popular retreat master in his day, Father Lovasik founded the Sisters of the Divine Spirit, a female religious order.