Although I am not a neurobiologist or evolutionary psychologist, I know that memories are valuable.  The pathways for forming and recalling memories depend, at least a portion, on the significance of the event seeking to be recalled.  Put another way, the more traumatic the event the more likely we will be able to recall it in memory.  You may not remember every walk in the park, but if during one walk you came face to face with a rattlesnake I'd bet you'd be able to remember that stroll!

For good reason.  Our brains are wired to perceive, analyze, and process threats.  Scientists often refer to the role amygdala play in this prioritization. These tiny pieces of grey matter living in our brain use more than half of their energy intercepting perceived threats.  In fact, the author Dan Goldman used the phrase an 'amygdala hijack' to describe overwhelming disproportionate emotional responses to perceived fear inducing situations. "I was overcome by fear".  

When you think about it from an evolutionary perspective it makes sense.  We had to remember where the tiger, snake, or other large predator lived for the sake of our own survival.  Thankfully, the days of encountering those types of threats at your desk or in the conference room are far behind us, but our amygdala haven't completely received the memo.  Our brains sill seek to remember threats and focus intently on fear rather than emphasize joy or positive feelings.

So what?

A fair point.  The crux of the matter is this.  If we are hard wired to prioritize the recollection of fear or thought of another way, the worst of our surroundings, it takes an act of will to rewire our brain to re-prioritize positive experiences.  Left to our own devices our brains would have us quickly recall the political shenanigans of a co-worker around promotion time last year before we recalled how six months ago that same person came to our aid when a family member was ill.  Its not that our wiring is wrong, its just that we need to continually work to keep our amygdala at bay and focus on what is the positive, rather than what is exclusively the threat.

A quick (somewhat dangerous and not safe for work exercise)

Get a pen and piece of paper.  Write down the first three coworker names that come to mind.  

Next, beside their names write the first memories that come to mind about each one.

How did you do?  Endearing memories, or threat based warnings?

Moral of the story.  Don't be hijacked into remembering only the ugly of the situations you find yourself in.  Take a bit more time and trust that there may in fact be a good memory that a needs a little more effort to recall.