Victory sells, defeat does not. However, you don't want your objective to be too easy, either, because if it's too easy, it's not likely to change anything in the way the system works.
La victoria vende, la derrota no. Sin embargo, tampoco quieres que el objetivo se consiga sencillamente, ya que sí es muy fácil, probablemente no cambie la forma en la que funciona el sistema.