Getting trapped in the dark swampy mess of your own thoughts is a horrible thing. You can sit there looking perfectly at ease working on paperwork while inside that brain of yours worry after worry and dark thought after dark thought just keep whizzing by in your mind, getting more and more intricate and involved as time goes on. Nobody can really tell that inside your brain, thoughts are flashing around crazily like the Tasmanian Devil on crack.
And there's no escape. There is no light at the end of this tunnel and if there is, it's probably just another horrible train of thought that is on its way to mow you down.
It's not like you can get away from your own brain and it's practically impossible to force yourself to not think about something. All you can do is try and distract yourself but what if the methods you have at your disposal aren't enough? What if the music lyrics you usually listen to as a means of diverting your mind just sets of new worries somehow? What if that calming audiobook suddenly makes you start to look more closely at the train wreck of a life your mind is insisting it is? There are only so many ways to attempt to derail the worry train when you're trapped at a desk.
The only thing that is worse than being on guard for nasty swirling worry vortexes is being on guard for nasty swirling worry vortexes on the inside while outwardly avoiding the various things that will set off a fellow employee's petty tantrums. You never realized how exhausting it can be to just be almost hyper-alert for an entire work day. Apparently sitting there all day with one ear open so you don't accidentally make them repeat themselves when they asks a question or so you don't make the monumental error of printing something out at the same time as they do can actually make you feel a bit physically tired. Who would've guessed that was even possible?
It might also be due to the fact that all muscles in your body seem to always be tensed to a slight degree whenever this person is in the room. Something that you don't notice happening until the few moments they leave the office and what amazing gifts those moments are.
Not that any of this worrying and tiptoeing will actually do any good. Somehow that person will find a way to be slighted. The minefield will level up and will be saturated with mines because in the three years you've worked here not one summer has gone by without this person screaming at someone.
Basically to sum up:
You've already got your own problems.
Your coworker takes their issues out on the people around them.
It's gonna be a long summer...