She thought the happiest moment of her life was when Henry woke up. When the kiss worked, when he took in a great gulp of air because he wasalive, he was going to live, and she loved him and he loved her and they could be together. Happily ever after with her son, the son she'd given up, the son she'd always wanted but couldn't care for. But now she could fix that, and they could have each other.
She thought the saddest moment of her life was when Snow died. Of course, her mom wasn't really dead, but for those few hours, she had no mother. She kept reliving the moment when the flame consumed her, when she couldn't see her, when something tugged in her heart, like the present was trying to pull at her while the past still kept her, like she didn't belong, because her mother was dead. Then Snow wasn't dead, and she pulled her into a hug, and Snow didn't know her, and she cried once more (but Hook brushed the tears away).
She thought the happiest moment of her life was when Hook told her about the Jolly. How he sacrificed his ship for her. His home. The one thing he'd always had for those three hundred years as he sought revenge. Probably the only thing he had left from his brother and his old life. And he had given the beautiful ship up for her, to find her, to bring her home, to save her family. He sacrificed everything to give her everything. And as he brushed his knuckles along her jawline, and gently tangled his fingers into her hair to pull her closer, and she felt his smile against her mouth—it was joy like she'd never felt.
She thought the saddest moment of her life was when she said goodbye to Killian. He stood in front of her, not close enough, because she wanted to pull him into her arms and never let him go. Because to let go is to give up, and she wasn't done with him yet. He whispered, his eyes looking sobroken, as broken as she felt, and then she took his face in her hands and pulled him toward her and kissed him. It wasn't exactly neat or beautiful, it was tear-streaked and messy, and he kissed down her throat when he pulled away, and she never wanted to leave his arms. But something was wrong, everything was wrong, and they had to fix it.
She thought the happiest moment of her life was when she pushed Killian's heart back into his chest. He placed his heart in her hands, his eyes sparkling but vacant, and she curled her fingers around it. In his current state he probably didn't realize the significance of what he did, but he literally put his heart in her hands, to do with it whatever she wanted. They quipped for a second, and then she shoved his heart into his chest, and there was a flicker of annoyance, and then his eyes met hers—and he was back. He kissed her, gently pushed her into the wall, and she'd never felt so loved in her life.
She thought the saddest moment of her life was when her father plunged a dagger into Killian's back. Evil Charming stood behind him, and before she could warn him—the dagger was in his heart. And suddenly her heart seemed to tear in two, like without him there was no point in living. She watched him fall, a scream on her lips, and her eyes never left his. It was then that she realized she loved him—so much—and he was dead. Her happy ending was gone.
She thought the happiest moment of her life was the moment that Killian spoke, from the balcony in the loft. Because he was alive and she had hope again and for those shining moments when they sat on her bed, whispering and exchanging little kisses and comparing fake memories—nothing was wrong in the world.
Maybe the happiest moment of her life was when Killian told her he loved her. He didn't use the exact words, but Emma knew what he meant. She knew what he had always meant, she'd known since Neverland, but finally she could accept his words and his kiss and his ring and the promise he wouldn't speak but was as clear as the happy shine in his eyes. Because she had him and he had her and they didn't need anything else.
She thought the saddest moment of her life was when she watched Killian die. She was the Dark One but she couldn't do anything to stop the blood pouring from his neck, she couldn't stop the life draining from him, she couldn't save him, she couldn't let the man she loved with all of her heart from dying. So she took them to the field where they'd been so happy just a few days before, and she poured darkness into him, because that would save him.
Maybe the saddest moment of her life was when Killian died in her arms again. He sacrificed himself for her, for her family, for her future—and she could do nothing, only hold the man she loved as he fell and died in her arms. Then they pulled him away from her and her parents held her back and if she couldn't have Killian—she didn't want this life.
She thought the happiest moment of her life was when she found Killian again. It was a bittersweet moment, tinged with sorrow by the cuts on his face and the blood soaked through his jacket and the eye that was swollen shut. But he was safe from Hades and so very nearly alive in her arms. And she could see a glimpse of hope, of the life that they could have in Storybrooke. With her pirate and her family, she knew that there was nothing she couldn't do, and he gave her hope. Hope to succeed and bring him home.
The saddest moment of Emma's life was when she left Killian Jones in the Underworld. In that moment, there was no hope. No light. No thoughts of a future together. No belief. She was leaving her True Love, the man she was destined to be with, to love and to cherish, to have and to hold, as long as they both should live. But his time was up—their time was up—she held onto his hand for as long as she could. But in the end, she's just a Lost Girl again without the only one who'd always loved her and believed in her and helped her and—breathing is impossible without the love of her life.
The happiest moment of Emma's life was when she heard Killian's voice behind her. His voice saying her name, so hesitantly, like she could be someone else. The moment when she turned and saw him. His eyes confused and concerned and yet so alive. She ran into his arms and kissed him, because she can see the light again. The light of a future together, the promise of a home and children and happiness and family together. She pulled away, kissed his cheeks and his forehead and his jawline and his nose and his lips again, because she was not going to let anything tear her love away from her again.
When he laughed and she kissed him again, it was like every sad moment was wiped away, and every happy moment exploded into color. And there was no more need to compare the sadness to the happiness, because she had her love now, and he would never leave her again.