Surely most of us have facepalmed at the thought of a humiliating event or a mortifyingly shameful moment at some point in our lives. These intusive memories may be a cause for discomfort but they're quite beneficial.
The reason why traumatic and bad experiences are easier to recall is because they serve as a perpetual reminder of our social misconduct. This is called 'involuntary memory' and it typically occurs within individuals after days, months or even years after the irksome experience has passed.
In evolutionary psychology, this is viewed as an evolutionary trait. Since the human being is a social creature our brains are hardwired to protect us from repeating actions that caused us harm--embarrassement in this case. Kind of like how we learnt that things that radiate heat could potentially burn us when we were toddlers still, by association. We associate heat with burning and so we refrain from touching or experiencing the object further. This is how we human learn, by associating experiences with outcomes.
What happens when we're feeling ashamed is we get a rush of Adrenalin through our veins and this drills the event in our memory and renders it so vivid that when we recall it it causes the almost the same amount of discomfort it caused the moment it occured.
The things that remind us of these experiences are so subtle, most of the time. You'd be sitting at the lunch table and a specific shade of yellow reminds you of that time you clumsily spilled red wine on your date's dress at the first date or the bad joke you cracked in attempt to loosen up the air but your date pitied your awkwardness. *cringes*
We don't want to risk doing the things that would alienate us over and over again and so we develepped ways to prevent that from taking place. It might at first seem like your brain is punishing you, but, in fact, it's doing all its best to protect us.