Maybe it was when your colleague cracked open a tuna salad at her desk despite your passive aggressive reminder that the aroma of fish makes you nauseous. Or when a passenger insisted on playing seven Justin Bieber songs in a row out loud during your hour-long commute. Perhaps it was the date who, instead of politely letting you down, cruelly ghosted you. You're not sure when it happened exactly, but people just seem ruder than they used to be.
The fed-up among us might point to Facebook for eroding our real-life interpersonal skills; apps like Tinder and Grindr for making finding a hook-up easier and more superficial; and the anonymity offered by websites like Twitter and Reddit which enable us to become heartless trolls. Even the US president is blurting out daily insults online now. And many polls seem to backup the hunch that good manners are dead.
Hilda Burke, a psychotherapist, and life coach, directs the blame at social media.
"I think people feel comfortable saying things to others via social media channels that they would refrain from saying in person," she tells IBTimes UK. "Trolling is the most obvious example of this. "Most of us when we see that our words are visibly upsetting another will temper them or back down to some degree but on social media we don't get those physical cues that our words are causing offence."
"It used to be that we all had the same rule book but today three main trends have changed the way in which we perceive courtesy and rudeness," chimes Dr Gary Wood Social Psychologist and coach, author of Unlock Your Confidence.
"In a multi-purpose society we come into contact with different standards that can be seen as rudeness when they clash with our own. The rise of the mobile phones divides our attention so that we are not always paying full attention to the people around us.
"Third, there has been a shift towards a more American individualism away from a European-type collectivism. So as a society we have become more 'me me me' instead of 'we we we'."
Except, it's not quite as simple as that. Rudeness is subjective. One person's accidental elbow in the ribs on the bus is another's intentional shove. It's hard to pinpoint whether our behaviour is really more rotten, if the internet has given us platforms to amplify the same levels of rudeness that always existed, or if we are just more sensitive.
One area, however, where studies have honed in on rudeness in a useful way is the workplace. A 2015 study at the University of Florida showed that in an office environment, a lack of manners is contagious.
And while what constitutes rudeness might differ, various studies at the university showed that people across samples and cultures react to what they perceive to be rudeness in similar ways.
"They [people subjected to rudeness] perform less well, they have difficulty thinking and making decisions, they are less helpful, and more stressed. Rudeness is disturbing and distracting to most individuals," explains Dr Amir Erez, who was a co-author of the University of Florida study, tells IBTimes UK.
Taking a second to consider how often we are intentionally thoughtless to others, then, offers some optimism. Although not much can be said for online trolls, we are usually rude because we are under pressure or our minds are occupied. In a funny sort of way, rudeness might even be something to unite us.
A recent study published in the European Journal of Psychology found that we judge rude behaviour as worse in others than we do ourselves. It's fine if we chat loudly on the bus, because we know it's a one-off. Those one-offs tend to accumulate to create the idea that everyone else is awful.
"Most humans are not rude by nature and few of us are rude by habit, but rudeness or impolite behaviour occurs occasionally, rather than constantly, and in those cases it is likely to be an expression of frustration or stress," Niels Eék, psychologist and co-founder of mental well-being app Remente, tells IBTimes UK. "What we perceive as an increase in rudeness in today's society may well reflect reality. However, it could also be linked to a rise in the external pressures of modern society, also leading to an increased sensitivity to certain behaviours."
And with that in mind, maybe we should be remember that being so hypocritical is really quite rude.