Just as nurturing our ability to love is a way of awakening bodhichitta, so also is nurturing our ability to feel compassion. Compassion, however, is more emotionally challenging than loving-kindness because it involves the willingness to feel pain. It definitely requires the training of a warrior.
Excerpted from: The Places That Scare You A Guide to Fearlessness in Difficult Times by Pema Chödrön pages 49