Once while in his court, King Akbar asked Birbal to write something on a wall that makes one sad when read in good times and makes one happy when read in sad times.

He took only a few moment and wrote something that fit the requirements. What did he write?

He write:
The time will pass soon.

If you read this line in happy times, you will be sad because you would want the happy time to last forever.
If you read it in sad times, you will feel happy, as you will feel optimistic about the future.