The key to the story here is that whether you can see it or not, everyone you meet is fighting a hard battle. The cashier at the store that you thought was rude might very well have been having the worst day ever after she woke up late, spilled coffee down her pants and lost her dog. That rude bitch behind you in line who can't move fast enough might be so rushed because doesn't want to be the mom late picking her kids up from school again. And finally, trust me on this, you do not need to complain or yell to the poor person at some store regarding the item that is out, the service that they weren't responsible for, or just straight up ruining their day in order to feel more in control of yours.
Perhaps, and hear me out, if we all start out with kindness, give each other the benefit of the doubt, and offer the effort to make someone's day we might all benefit from the slight adjustment in perspective. The next time you are frustrated with someone, try and imagine what battle they are fighting and even though it is imaginary, you may find yourself being more willing to show patience, kindness, and earn some good karma for your own hot mess day.