A/N: Just a little one-shot to follow on from my story 'Lilies Don't Grow in the Dark'. Exploring Snape's remorse for his choice to put the death eaters over the one person who loved him.

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The day Lily Evans walked away from Severus Snape was the darkest day of his life.

Lily had been a light, a beacon of hope, a representation of all the best parts of himself, since he was nine years old.

She saw him in a way no one else did. She saw him as pure, whole and vulnerable.

But he couldn't be vulnerable. He had to be strong. He had to fight. To be invincible. Unconquerable.

And that is why he joined the death eaters.

Lily had never understood. She was gentle, soft and tender like the flower she was named after. She didn't need to fight like he did. Her place in life was already made.

People loved her.

No one had ever loved Severus. His mother might have said she did, but if she had, why hadn't she done more to protect him?

He was what his father had always said he was. Weak. Nothing. No one.

And so he needed to be someone. He needed to be strong. He needed to fight.

"I don't understand you." Lily had said, that last conversation they'd had as friends.

She'd been so beautiful and so young. She'd had her whole life ahead of her.

Severus knew she'd held herself back for him. He knew her friends hadn't liked him. He knew he had a dark side Lily could never understand.

He'd let her go. Though it had tortured him to watch her with James Potter, he hadn't fought for her any more. She was better off without him. She didn't need to go where he was going.

His missions with the death eaters were brutal. He'd known it would be difficult. Change never came easy. But there was a difference between cursing Potter and his gang in the corridors at Hogwarts and doing so on a terrified muggle family.

Fortunately the other death eaters seemed to have no such reservations and his cowardice went unnoticed.

And then he made the greatest mistake of his life.

He sold Lily Evans, now Lily Potter, to Voldemort.

His heart broke into a thousand pieces to think about it. How could he have done it? How could he have led her to her death like that?

Lily had been the purest, gentlest, most beautiful creature he'd ever known. She'd loved Severus for who he was. She'd been the only one.

He didn't want to live any more. A world without Lily was a world he didn't want to inhabit.

And what was worse, he had killed her. He had extinguished the one flame that had given him hope in the goodness of life. The one soul who had seen him for more than what others did - a soulless creep.

And now she was no more. How could he go on?

"Her son lives." Dumbledore told him when they met at the top of a hill that fateful day he found out what Voldemort had done.

Severus knew Dumbledore never really forgave him for his mistake, but the man needed him. Severus was in the perfect position to help.

"You can protect him."

Severus nodded. He had lost his beloved Lily, but she lived on in Harry Potter. She had sacrificed herself so that he could live. It was all he had left of her. He would honour her until his dying day.

It wasn't easy. All he saw in Harry was his father. But the longer he spent working as a spy for Dumbledore, the more he could see what a fool he'd been.

There were dark times. He would sit alone in his parents' old house in Spinner's End and feel as empty and hopeless as the glass bottles on the floor he'd worked his way through.

He'd thrown away any chance of happiness for himself, and he knew he must live with that for the remainder of his days.

He didn't matter anymore. Harry was all that mattered now. And he would gladly sacrifice his life for his.

He wondered if Harry would ever know what he'd done. He wondered how much more the boy would despise him when he found out. It was because of him that he no longer had a mother.

But, if he could do anything, he would live to ensure Harry's life was nothing like his own.

He wouldn't waste it.