"No!"
"Stop!"
"Please!"
Everyone is crying out to Emma, but no one can reach her. All of them are repelled by an invisible, magical source that radiates from her. It is love: it is strength. Her hand is over her chest, and her intentions are clear.
"Mom!" Regina is holding Henry: not holding him back, but holding on for dear life.
"Emma!" Snow's cries are as anguished as when she heaved Emma into being, and she and Charming are fighting desperately to get to her. "Emma, stop!"
Everyone is crying. The savior is no exception. No one had known that it would come to this. After the curse had broken, the people of Storybrooke had slowly realized that they were all dying. They couldn't survive in a world without magic. They had to go back, or they would perish.
That's why Emma has to do this. Her hand is plunged into her own chest. She's never taken a heart before. When she draws it out, everyone—her parents, her son, and Regina—quiet for a moment.
Emma remembers telling Cora that love is strength. She hopes that she has enough of it to get everyone back safely.
"Please." Snow White whispers.
"I have to save you. It's the only way." Emma begins to squeeze. Her eyes are on her son. Her lips move. I love you.
In the next moment, her heart is dust.
The energy around Emma bursts, and Storybrooke is no more.
xxx
In Fairytaleland, Snow White wakes up in her marriage bed, and draws a ragged breath.