Human life inherently has three things: Our own work, people's work, and God's work. The trouble is that most of us spend 80% of our time on the last two things, and then are surprised why our work is as messy as a student's rented room. A female colleague can spend the whole morning "analyzing" her boss's psychology, analyzing each frown whether it's due to pressure or because her wife doesn't give her pocket money, but in the afternoon she lets her personal work make mistakes because she loses focus. A friend takes care of God's work, complains to the end of the world when he sees harsh sunshine, fears climate change when it rains, while forgetting about buying milk for his child.
In fact, worrying about other people's affairs or earth and sky affairs is a sophisticated way to delay facing oneself. Worrying about people's affairs is easy because no one tells you to correct mistakes, worrying about God's affairs is even easier because no matter how much you worry, nothing can be changed. Only your own affairs are the most difficult, because it requires real action and real responsibility. Like the story of a person asking a monk if he should give advice when he sees others living wrongly, the monk only asks back: "Have you lived correctly?". If you have not lived correctly, no one will listen to your words. If you live correctly, people will see and reflect on you.
Knowing the boundary is not indifference, but stopping turning someone else's life into a "personal project" and accepting what is out of control to save energy for what can be done. If life is a table, each person only has one chair. Sitting in their right place is already a great success. Don't try to run to someone else's chair to instruct, and don't raise your head to argue with God for exhaustion.
Returning to the cup of coffee, amidst the noise about the "fate of the world", he opens his laptop and starts working. These things are sometimes boring, like cleaning up life or keeping a promise, but they are the real foundation. Not great, but that is the only thing if you don't do it, no one will do it for you. And that, perhaps, is the most practical form of peace he finds in the chaotic city.
