Don’t do it. Nothing good comes from thinking and thinking and overthinking shit that happened ages ago. If someone did you wrong or hurt you in some way, the only thing that’s going to happen from you sitting there and thinking about it is that you’re going to feel stressed and angry and hurt. Don’t invite needless negativity into your life. To quote Elsa, “Let it go.”
And definitely don’t throw that historic shit back in someone’s face ages after it happened. That’s just low. If you have a problem with someone, tell them as soon as possible. Like if your friend was rude and obnoxious to you at a party and didn’t apologize for it afterwards, don’t just sit there and let those negative thoughts and feelings fester and then unload on your friend half a year later. Wait a day or two to get your thoughts and words in order, and then talk to them.
Bottom line: If you’re going to say shit, say it while it’s still relevant. Not saying anything while thinking a bunch of shit about the person only to finally complain to them months or years later is like applying for a job months after the application was due – unwanted and tacky.