The narrator is breaking up with his girlfriend. The irony is that she, not him, was the one who knew what they had wasn't working. But for whatever reason -- she might have thought things would get better, or maybe she was looking out for his interests -- she hid that knowledge, and kept what they had going.
But the narrator finally comes to the conclusion that the girl had already reached: the relationship won't work. So he tries to act like he's the only one who wants it to end, and tries to comfort her by telling her to "get back on that horse and ride." As if there's someone or something out there, better than him.
The narrator is breaking up with his girlfriend. The irony is that she, not him, was the one who knew what they had wasn't working. But for whatever reason -- she might have thought things would get better, or maybe she was looking out for his interests -- she hid that knowledge, and kept what they had going.
But the narrator finally comes to the conclusion that the girl had already reached: the relationship won't work. So he tries to act like he's the only one who wants it to end, and tries to comfort her by telling her to "get back on that horse and ride." As if there's someone or something out there, better than him.