Minimalist with stoicism- Examine your impressions

So make a practice at once of saying to every strong impression: ‘An impression is all you are, not the source of the impression.’ Then test and assess it with your criteria, but one primarily: ask, ‘Is this something that is, or is not, in my control?’ And if it’s not one of the things that you control, be ready with the reaction, ‘Then it’s none of my concern.’(Enchiridion I.5)

Think of an event, people, criticisms or insults being thrown at us, am I able to control? If not, then stop doing anything about it. Things beyond our control is useless for us to change. 

I guess it's another way to minimise things you can do to change things or not.