For Failure and Setback 

Failure is the mother of success.

It is always darkest just before the day dawn.

The miserable have no other medicine but only hope.

In all things it is better to hope than to despair.

If at first don't succeed, try, try, try again.

Preference is falling nineteen times and succeeding the twentieth.

If you fail, make failure a stepping stone to success.

Adversity often leads to prosperity.

The good seaman is know in bad weather.

Affliction（痛苦） and adversity make men better.

He laughs best who laughs last.

Fortune favors the bold.

For man and master of his fate.

Nothing is difficult for one who strives.

To strive, to seek, to find, and not to yield（屈服）.

Adversity reveals genius; fortune conceals it.

Nothing in the world can take the place of persistence（坚持不懈）.

Energy and persistence conquer all things.