Marcus Aurelius · Meditations VIII.17
If you can, correct the cause; if you cannot, correct the thing itself; if you cannot do even this, of what use is it to find fault? Nothing should be done without a purpose.
What this means
Marcus lays out a simple decision tree: fix the cause, or fix the thing, or, if neither is possible, stop complaining. Fault-finding without a remedy is wasted motion. The closing rule, do nothing without a purpose, is the standard he holds every action to.
On control, work, reason.