Old man and the horse

Disaster and blessing are born of each other and their transformation is hard to predict. Blessings can become disasters, which can then transform into blessings. The change is never ending, and its mystery is forever unrevealing.
Here is a nice story that illustrate it nicely.
Source: "Lessons in Human Life" in "Huai Nan Zi," compiled by Liu An (179 - 122 B.C.)

There once was an old man who lived at the northern border of the state. He was skilled at raising horses. One day he discovered that his horse had disappeared into the neighboring state of Hu. Neighbors felt sorry for him, but the old man said, "Who knows if this will turn into a blessing?"
A few months later, the missing horse suddenly returned, bringing back a fine horse with it. Neighbors came to congratulate the old man on his good luck. But the old man said, "Who knows if this will turn into a disaster?"
His son loved riding the fine horse, and one day he fell off the horse, broke his legs and crippled himself. Neighbors came to comfort the old man, who replied, "Who knows if this will turn into a blessing?"
A year later, the neighboring state of Hu invaded, and all the young and strong men were drafted to fight the war — nine in ten ended up being killed. The son, being crippled, stayed home and his life was spared.