So I made a thread kind of similar about people having regrets for no real reason, and I'll just vent on none other than a lego forum that is basically PG-13 4chan.
I tend to hold grudges for long periods of time. Generally, if you act violent, rude, or generally douchey towards me in particular extremely often, I'll remember that, and act the same towards you. It's eye-for-an-eye punishment, sure, but I cannot help myself from doing such things. I can't just let them mouth off at me and crack snide remarks behind my back* (I HATE when people do that stuff) but I can't unleash all my pent-up anger on them either. It's a lose-lose situation, and ignoring it won't help (see *) I try to talk to adults or close friends about it, but they either side with them without hearing my part, or be too lax about it and release me, with the person who I reported going right back to his starfishry in the blink of an eye.