When you work with machines, there will always be a solution to a problem. Even if it seems impossible, even if you don't have the correct answer, you will always somehow find it.
When you work with people, there will always be a problem for any solution. Even if it seems to be the most posible simple thing, even if you have the correct answer, you will always find yourself in the wrong.
"But machines aren't perfect, they fail all the time"