The speaker is mourning a relationship that has gone cold while the other person is still around. It begins with one perfect night, a dream come true, and the broken line "my. fucking. dream." shows how much it meant and how raw the feeling still is. Then the mood crashes. The speaker is angry at themselves for still writing about it, even wishing to disappear, which suggests how heavy the loss feels.
The second half is flatter and more painful. Arguments, short texts and silence replace the closeness of two people who once "told each other almost everything." The line about watching the other person walk away more often than they come forward shows who seems to be doing the reaching out. The ending turns the idea of winning upside down: if the fading-apart becomes a contest over who forgets first, the speaker doesn't want to win. The mood is bitter and tired, but underneath it is clearly love and a refusal to let go.