With that in mind, I hope I can tell you a story I read in a book called "White Gold" about Barbary Corsairs capturing slaves from Northern Europe (by Giles Milton) ...
There was once a tyrannical and cruel sultan (of Fez or Marakech perhaps, can't recall exactly). He ordered his slaves to build a huge and long wall between two palaces. Dig the required materials, bake the clay-like bricks, and build the wall. It took a LONG time. When it was completed he ordered the slaves to destroy it completely, pulling down the wall and grinding the bricks back into dust. That was HARD work. Then he ordered them to build it again exactly as it was before in exactly the same place. A very brave courtier (the sultan had a habit of testing the sharpness of his blade on random courtiers' necks!) asked him why he had done so. The sultan honoured him with an answer: "When you have rats in a sack you have to keep shaking it, otherwise they will gnaw their way out!"