I know I can get pretty mean when someone disrupts me from what I'm doing. That's why I really hate working retail and hope to be able to escape it forever. There is nothing more irritating than working on a project and then having customers come in (despite the fact that I actually get more money dealing with customers).
I do get irritated explaining myself, but I think it has more to do with my memory getting flustered when under pressure than anything. But actually it is already known that people do not think rationally when irritated or under pressure and it is best to wait a bit before doing something under those conditions.

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"Man lives in the sunlit world of that which he believes to be reality. But unseen by most is an underworld, a place that is just as real... but not as brightly lit... A DARK SIDE!"
-opening from Tales From the Darkside