I read this in Jack Kornfield's The Wise Heart: A Guide to the Universal Teachings of Buddhist Psychology:
pp. 32-33 [boldfacing added]
Living with compassion does not mean we have to give away all our possessions, take in every homeless person we meet, and fix every difficulty in our extended family and community. Compassion is not co-dependence. It does nto mean we lose our self-respect or sacrifice ourself blindly for others. In the West we are confused about this point. We mistakenly fear that if we become too compassionate we will be overwhelmed by the suffering of others. But this happens only when our compassion is one-sided. In Buddhist psychology compassion is a circle that encompasses all beings, including ourselves. Compassion blossoms only when we remember ourself and others, when the two sides are in harmony.
Compassion is not foolish. It doesn't just go along with what others want so they don't feel bad. There is a yes in compassion, and there is also a no, said with the same courage of heart. No to abuse, no to racism, no to violence, both personal and worldwide. The no is said not out of hate but out of an unwavering care. Buddhists call this the fierce sword of compassion. It is the powerful no of leaving a destructive family, the agonizing no of allowing an addict to experience the consequences of his acts.
Wherever it is practiced, compassion brings us back to life.