"My biggest challenge over the years was remembering what to do in each place as the security people at the airports had a tendency to get upset if you didn't do it their preferred way."

It can differ from airport to airport. I traveled from Ottawa to Toronto often enough for it to be mindless but differences between two national airports in same province of same country on same airline still caught me if I went too much on autopilot.

And then I'd fly to Halifax and all my instincts went out the window :).

Sometimes it'd differ shift to shift. Agents would get mad at me for taking or not taking tablet from my bag. Mentioning "your colleague instructed me otherwise, can you kindly confirm the rule so I can comply in future" only gets you marked as belligerent - the power trip is definitely there :-/