All of us have the potential to develop that kind of compassion, because whenever we see people who are suffering, especially those close to us, we immediately feel empathy towards them, and witness a spontaneous response within our minds. So all we have to do is to bring that potential out, and then to develop it to become so impartial that it can include all sentient beings within its embrace, whether friend or foe.
To cultivate this great compassion within ourselves, first of all we need to develop what is called loving-kindness, a feeling of connectedness or closeness with all living creatures. This closeness and intimacy should not be confused with the kind of feeling we normally have toward our loved ones, which is tainted by attachment...ego and selfishness. On the contrary, we are seeking to develop a feeling of closeness towards other sentient beings, and affection for them, by reflecting on the fact that suffering is inherent in their very nature, on the helplessness of their situation, and on the instinctive desire they all have to overcome suffering.
The greater the force of our loving kindness towards other beings, the greater the force of our compassion. And the greater the force of our compassion, the easier it will be for us to develop a sense of responsibility for taking upon ourselves the task of working for others. The greater that sense of responsibility, the more successful we will be in generating bodhicitta, the genuine altruistic aspiration to attain buddhahood for the benefit of all.
--from Dzogchen: The Heart Essence of the Great Perfection by His Holiness the Dalai Lama, translated by Thupten Jinpa and Richard Barron, Foreword by Sogyal Rinpoche, edited by Patrick Gaffney
