What I say to my small daughter when she’s nine: Kids can be jerks but the best thing to do is to forgive them, even if they’re not sorry.
What I will say to my small daughter when she’s sixteen: You should forgive people even if they’re not sorry because those people sound like real assholes and it will piss them off like crazy if they realize you’re forgiving them for being the dickheads that they don’t think they are. Even better, just walk up to them and put a hand on their arm and say, “I forgive you.” Then walk away. And then you can feel better because you’ve fucked those assholes right in the head. And also because forgiveness is next to Godliness. Or cleanliness. One of those.
Regardless, forgive them and you win. Even better, forget them completely and then keep introducing yourself to them so they realize they’re not important enough to remember. Then look at the note you wrote on your arm which says “Stop saying hi to Potato-face. She’s an asshole to everyone and you always forget that.” Then nod to yourself and say, “Oh. Sorry, Potato-Face. Never mind” and walk off. That way Potato-Face realizes that you’re trying to being polite and gracious. And that’s important.