This is the part where they aren't together.
She has spent three hours taming her hair and spent three paychecks on this dress, and he's waltzing with a young woman in red whose flowing black hair sways perfectly in that way Hermione never could get her hair to. Stay, she had asked him, please, it can't be more important to you than we are. It could, though, and so there she was, holding her knees to her chest in a deserted alcove and drowning in her disappointment in herself. She should have been enough, she should have been enough, she should have been enough.
This is the part where she remembers the good times.
She catches a whiff of his cologne one day as she's hurrying through Diagon Alley, late for lunch with the Minister. She has no time to stop, but she finds herself sprinting through deserted hallways, snatching kisses and holding hands with an unexpected ally, reclaiming Hogwarts as their own from the misery of their pasts. She leaps forward, still holding the memory of his hand in her own, all the way to the restaurant where the Minister is waiting for her.
This is the part where she remembers the bad times.
It wasn't easy, and she had never expected it to be, but times immediately after the war were uncertain and for a Death Eater's son to hold Hermione Granger's hand was a good way to get himself killed. She hid around corners while he convinced those who wouldn't accept them that she was a plaything, disposable, before he turned the corner and pulled her into his arms. She said the tears were from laughter, and maybe one day she would laugh about this, but at eighteen it burned her love-charred heart.
This is the part where she sees him again.
She's in the back of a bookshop and laughing at some of the more entertaining reviews of her latest book, because they're truly hysterical some of them, when he's there. She doesn't seem him at first, but there's that cologne, and that funny little speed walk he does when he's concerned, and then there he is. Peeking through a shelf she sees him slumped against a wall, eyes closed, breathing heavily, and suddenly he looks so similar to how he did as a teenager running away from Argus Filch that she cannot help but to laugh. He opens his eyes, and looks around, hopeful, but the spell is broken. She is in the present now, and the present is not funny, so she stops laughing and he walks out.
This is the part where she feels regret.
After the war when she was broken down it was him that she rebuilt herself with and now, now that he's gone, she feels him in every laugh and smile and dance, and she wishes he wasn't there because she doesn't want those things to hurt. He's always there, always hurting, always reminding her of what he was to her. She still can't bring herself to wear red.
This is the part where she loves him still.
She's getting married, and she's so in love with Oliver that she doesn't know how to handle herself, but she's worried about their first dance. He will be there, is always there, when she dances, and that makes her want to dance even more. She's terrified.
This is the part where Hermione walks down the aisle.