Picture this ....... you're on the bus reading quietly and someone on the bus is whinging loudly about something outside of their control. You try to continue reading but a good part of your attention is listening to their whining. You grow increasingly frustrated at their apparent lack of wisdom and you consider offering them the above quote to help them out of the futile (& loud) conversation their ignorance has them in and earn yourself a bit of peace for the rest of the bus ride.
I would suggest there's (at least) two conversations happening here. One between "the whinger" and his friend and another in your head. If you accept this second conversation is the one causing you frustration you may realise that you need to heed your own advice (in this case the above quote) for letting someone else into your sacred space.
It's often easy for us to see lessons that could help others and often it's precisely the lessons we would prescribe others that would actually serve us.
Master your own domain before you try to "fix" the world around you.
It's the height of hypocrisy and arrogance to assume you can fix in another what's broken in you.
Next time you feel frustration toward another ask your self two questions
1. Does "their" fault live with in you?
2. Could the energy and attention you spent allowing yourself to be frustrated by them be redirected to something more positive?
The second questions is the antidote to most things we worry about these days and one of the keys to self mastery and personal freedom.