The philosophy of yin and yang describes how opposite forces are interconnected in the universe. Without darkness(yin) there can be no light (yang), without cold there can be no heat, without good there can be no evil, etcetera. Opposites must exists to provide a point of reference and comparison.
With this in mind, I believe the greatest challenges represent the greatest opportunities. Those hardships which challenge mankind the most, represent the best opportunities for mankind to unite and come together.
When you are faced with a great challenge in life, think of the great opportunity presented. For example:
The United States economy is in a recession:
Yin: People are unemployed and struggling to put food on the table.
Yang: People now have time to spend with their families and are growing gardens in their yards.
Housing prices has fallen by 20%:
Yin: Families have lost their life savings in their biggest investment.
Yang: Properties are now affordable once again. Families look at their homes not as an investment, but as a place to raise a family.
Identify the great opportunities created by your great challenges.