The mill gains by going, and not by standing still.

Understand the thought

Meaning in plain English

A mill produces through operation, not merely by standing ready. The image contrasts having the means to do something with putting those means to useful work.

What the words are saying

The mill’s presence alone does not produce its gain; movement makes the difference. In another setting, owning equipment or making a plan is not the same as carrying out a task. Ask which useful step turns preparation into an actual result. This is not a claim that constant activity is always productive. Maintenance, rest and checking conditions may be necessary before operation. The relevant contrast is purposeful action with unused readiness, rather than movement for its own sake.

Everyday example

A reading group begins the agreed discussion instead of spending another meeting rearranging a plan that is already workable.

When to use it

Use it to identify the useful action that turns readiness into a result.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.