I am a chronic interest-loser. No matter how exited I am at the start, I end up losing interest. There's something wrong with me: an over active novelty-seeking lobe, or something. I believe that and I swear to you that I am the first human who uttered the phrase "It's not you, it's me." It came to me during a confrontation over thirty years ago, long before Seinfeld existed. I think the girl must have told so many people about this baffling, unanswerable utterance, that news of it spread till it got to the ears of the Seinfeld writers.
I have no idea how to dump someone though. I mostly dealt with it by just trying to see them less and less and less in the hope they'd kinda forget I existed.