From last sem's FWS:
Whereas love is the desire for others to be happy, compassion is the desire actually to bring about their happiness by freeing them from their suffering.
Compassion is not the sad, anxious feeling we often experience when we see or hear about people's pain. Neither is it a sentimental involvement in their problems nor, on the other hand, a conscious holding back. All these responses are inappropriate and show that we do not understand the causes of the problems, or the solution.
- From How to Meditate: A Practical Guide by Kathleen McDonald