Thich Nhat Hanh writes in Calming the Fearful Mind: A Zen Response to Terrorism:

The Kingdom of Heaven is like the blue sky. Sometimes the blue sky reveals itself to us entirely. Sometimes it reveals half of itself, sometimes just a little bit of blue peeks through, and sometimes non at all. Storms, clouds and fog hide the blue sky. The Kingdom of heaven can be hidden by a cloud of ignorance or by a tempest of anger, violence and fear. But for people who practice mindfulness, it is possible to be aware that even if it is very foggy, cloudy, or stormy, the blue sky is always there for us above the clouds. Remembering this keeps us from sinking into despair.