How do you make sure that mistakes don't happen, then? Do you blame and fire people who make mistakes, and hope that the next person put in the same spot doesn't make a mistake? Or do you figure out what caused that person to make the mistake and ensure there are processes in place so that next time this is less likely to happen?

Extrinsic motivators like 'we will give you a bonus' or 'we will fire you' are surprisingly bad at getting people to not fuck things up.