Titles within the Wheel of Time series don't necessarily reflect a specific event or object within the books. For instance, there's still some speculation regarding the meaning of Crossroads of Twilight, and even Towers of Midnight has multiple meanings.
In this, we're given the quote "The sweetness of victory and the bitterness of defeat are alike a knife of dreams."
So, this means that sweetness of victory and bitterness of defeat are likely common themes throughout the book.
We do see that there are some major victories within the book:
- Elayne takes the throne
- Perrin finally reunities with Faile
- Rand defeats Semirhage
But, we also see some bitter sides to the same edges:
- Elayne's victory was hard-won, and incurred a great deal of debt to Andor (and did nothing about the Black Tower)
- Aram attacks Perrin, ending in Aram's death
- Rand loses a hand to Semirhage, she tells him about his problem with Lews Therin, and because it was Semirhage, not Tuon, he didn't have the intended meeting with the Daughter of the Nine Moons
Now, these are just a few examples of the events that match the theme. I personally see a great match in the Perrin/Faile events. He's been trying to rescue her for several books. In the end though, this victory is bittersweet:
- Aram dies, corrupted by Masema
- Perrin accidentally kills one of the Aiel that helped Faile
- The Shaido retreat, leaving them as a potential future complication