To me, this songs means empowerment and finally telling yourself that you are able to move on.
Its about finding your ex and seeing that they have moved on,
and you, being optimistic/stubborn/determined or what you want to call yourself, think you can convince them that you are still the one, only to realize that you are wrong.
And even though you realize you can't have them, you simply tell yourself and possibly them that its not impossible, but you'll find someone like them. Not specifically like them, but someone to share memories and moments with and to give you that remarkable sensation of love.
She's not wishing bad things upon her ex and his new love, she just wants him to remember their love, memories and what they shared.
Its quite beautiful. This song is truly a bittersweet goodbye.