"Stick to the rules no matter how silly or unimportant they may seem to you"
What if we are following the rules? I take a bag that was perfectly acceptable in ten airports but on the eleventh it's suddenly not compliant. I have to take my shoes off at the security in BRU but the rest of Europe doesn't give a rats arse about shoes, you just go through the detector. More often than not I see people going through with empty bottles of water, but if you have 10 drops left in it, it goes in the bin. Years ago, some airports were demanding you would turn on your laptop at security (because if it's a bomb, it's better to kill people at the airport than on the airplane, right?), and my boyfriend almost didn't fly one day because his battery was not working, and the laptop wouldn't turn on without the electrical cord...
There is no consistency in security checks, and this leaves passengers with the constant worry that something will go awry despite best compliance and preparation. How do you prepare for randomness?...