You’re reading a romance novel or one with a major romantic subplot and then the designated love interest of the female (or male) protagonist does something that hurts the protagonist and you hate them for it, and wish they didn’t end up together… but sure, they end up together.
Due to the nature of this discussion, spoilers from the books are included.
Example of how to write:
Gideon de Villiers from The Ruby Red Trilogy.
>!spoiler here!
Michael Scott Rohan’s The Winter of the World is a great fantasy series, but the protagonist’s entirely superfluous enfatuation with Kara is uncritically written as love destined in the stars, which annoyed me to no end.