I find the #1 cause of stress at airports is dealing with incompetent airline/airport employees who cannot be bothered to properly follow the rules.

All I want is a predictable and consistent experience every time I fly and stand in as few queues as I can.

This means, airlines need to invest in friggin' bigger bins, so more carry on bags can be accommodated, if power outlets are going to be installed, it should be nose to tail fleet wide, not a half @$$ed effort where it's on some planes, and only in premium cabins on some other planes.

Lounges, need to simply have consistent and logical admit policies that are highly predictable and not based on the mood of each individual agent.

The whole experience just needs to be more consistent and predictable, that would solve about 90% of the problems that cause air rage.