True, it's natural/cultural for French people to complain all the time about everything while I know a lot of Chinese people who almost never do, even if they want to. They smile while their minds are full of complaints.
Talking about that, short question: Is the complaint has to be said out loud to be counted or you also consider it a complaint when you already have it in your mind? 
We will consider both. Cuz the ultimate goal is to train the way we think and react to something that we might complain about. But it's totally up to you.
Thank you for the answer. It makes sense :)