Guard your heart and pray for others for this is the best way to love one another.
Guard by every means your heart, or the sincerity of your heart, your capability to sympathize with your neighbors in their joys and sorrows. And avoid, as you would avoid mortal poison, any indifference, and coldness to people’s various misfortunes, sicknesses, and needs: for it is by sympathy, especially active sympathy, that the love and goodness of the Christian are revealed. And in love the whole law is contained. Whilst, on the contrary, our selfishness, malice, malevolence,* and envy are revealed by a want of sympathy.
Thus, pray for all those for whom the Church orders you to pray. Or, pray willingly for others, as you would pray for yourself, and do not relax in sincerity. Do not lose inward respect for the person or persons for whom you pray. Do not allow the Holy fire of love to be extinguished, or your light darkened. Do not despond at the wiles of the enemy, undermining your heart and striving to implant in your heart aversion to all, to take away from your lips the prayer of others which is the best proof of evangelical love for our brethren.
– St John of Kronstadt, My Life in Christ
1 having or showing a wish to do evil to others.