Recipes for serenity, chapter 1: sphere of direct control

The recipe for serenity is quite easy, and it has ancient roots. The concept is simple, its logic unassailable, for it is very basic. Yet few people follow it. The others, almost everyone, spend their days at work, at the restaurant, at the bar or at home, arguing about topics they actually know nothing about; matters that are not directly connected to their lives. And they do it with such a zeal, as if they were defending what is dearest to them.
Let's try to make this point clearer.
You come across a theory, a hypothesis, a suspicion of a global nature. Let's say in the geopolitical, financial or social context. Okay, may be that theory is correct. Or maybe not. Can you confirm it or deny it without leaving your sphere of direct control? If the answer is yes, then confirm it or deny it. If the answer is no, I'm sorry, but by insisting on supporting it you are only wasting time and energy, and you are probably making a fool of yourself on top of that.
Let's take an example.

Developing country? - Bangkok, Thailand

When disabled passengers enter any station of the Bangkok SkyTrain system (BTS), they are accompanied by an attendant to the right platform and assisted while boarding the train. The arrival station is then informed of the relevant train, car, door and seat numbers. When the passengers reach their desired destination, an employee will be waiting for them in front of the specified door and will accompany them to the station exit.