Known cost: extra checking, extra work

Hidden cost: no learning, no improvement

We can't know in advance if a potential problem is real or imagined.

The only way to know it to not prevent it, and monitor whether it happens.

If we always try to solve all potential mistakes before they happen, we will never know which actually happen, and which didn't.

Preventing a potential problem that won't actually occur, is waste. We waste the efforts made to prevent it. And we will never learn to reduce this waste. Until we learn to allow for potential mistakes to happen.

This doesn't mean we should allow all mistakes to happen. Some could be very serious. But most aren't.

Eg. We do take regular, automated database backups, even though we never need them. We probably never will. But that's a risk we won't take.