The mill cannot grind with the water that is past.

What has already passed cannot be used to power present action. The saying urges attention to what remains possible now, rather than relying on a chance, resource, or moment that has gone by.

It can counsel acceptance when a loss or delay has left necessary conditions unavailable. It does not mean that every past mistake is beyond repair; rather, regret alone cannot restore what is no longer available, so one must adapt to the circumstances still at hand.

Use it when someone keeps looking to an expired opportunity or a resource that can no longer be recovered. It suits reflective advice about moving forward, but may sound dismissive if offered too quickly to a person facing grief or serious loss.