I think it was just how self obsessed Carrie was, imo and made everything go back to her problem. She also went to great lengths at times to try to control what people said/thought of her because of her bad behaviours. Examples I can think of:
Big always made it clear who he was in the early days and Carrie just tried to change that and rush things when he clearly didn't want to. Even stalking the church he took his mother to (the impression was he enjoyed that time with his mother and wasn't a "Carrie" focused moment). She also stalked his ex wife and made up some story to pitch a book idea to her!
She then whined/spoke constantly to her friends about the break up until they sent her to therapy. Then the next year went back for more!
Had the affair with Big, then on hearing he and Natasha split she had the cheek to find out where Natasha was having lunch (after it was made clear Natasha was never going to return her call) to go and "apologise" to her, only it was only ever about mending "her" bad karma, not because she was actually sorry.
She made a big deal of getting Aiden back then pushed away all attempts made by him to move forward (engagement/moving in) like a normal relationship. I know people said Aiden was trying to force her into these things, but he was just being normal wanting marriage/live together. She even invited Big to his country house!
Miranda called her out a few times, notably with "the bullshit bagels" Carrie brought over as a ploy to talk about Aiden and their argument when Carrie was meeting Big for lunch and Miranda argued she keeps going back for more.
When her and Aiden split the first time after the affair, Carrie didn't seem upset at all in the following episodes or even mentioned Aiden! She just had a few dates/shags with various guys and Aiden only gets mentioned again when they see him and Steve in the street having a drink together. Then the first thought is 'oh they must be talking about us!' (they weren't, they were with their new girlfriends).
Also when she stalked the "face girl" so she could tell her not to judge etc, and that's when stanford calls her out for talking about that woman for 10 blocks yet just says "nice" when he asks her opinion on his new boyfriend!
Oh and having a go at Charlotte for not offering to lend her the money to buy her apartment!
So many! I'm sure there's loads more examples!