"Edmund, son of Adam, come and follow me." Aslan said as he motioned with his head the direction they were to go. The two of them walked in silence for a while, until they were out of hearing. "Do know why I wanted to talk to you Edmund?"
"To punish me, like I deserve."
"No, to teach you. Those who do wrong can chose to either do wrong and wrong again; or repent, ask forgiveness and be forgiven. Then learn from that wrong, accept it, change what needs to, and use what you have learned to better yourself and help others. You are forgiven, understand that, reflect on this and put the event behind you."
"Why forgive me?"
"Do you know what you did was wrong?"
"Yes."
"Did you regret what you did?"
"Yes, almost immediately."
"Do you want to be forgiven?"
"Yes, very much so."
"Can you learn from this?"
"Yes."
"Do you think you can learn to forgive yourself?"
"I-I think I can."
"Good, you will do many great things."
"Aslan? Do you think Peter, Susan and Lucy will forgive me?"
"That you will have to find out yourself." Aslan said as they came up to his siblings. "You needn't speak of what is past." He said to them all.
"Oh Edmund we're so glad you're okay!" exclaimed Lucy as she launched herself into Edmund's arms.
"Ed, it's good to see you looking more like yourself, I missed you baby brother." Peter said.
"You had us all so worried. Let's go get some breakfast." Said Susan kicking into mothering mode.
With that he knew one day he would be able to forgive himself. But first he had to practically die and wake up to his brother and sisters surrounding him. Then he learned that Aslan died for him, he realized that just like him, he would die for his family. At his and his siblings coronation, hearing their subjects cheer for them and some of them telling him thank-you for breaking the witch's wand, he forgave himself more and more.
Within five years he almost completely forgiven himself; there were, of course sometimes when he felt guilt but they were becoming fewer and farther between. By the time they found Prince Cor, he had forgiven himself as much as he ever would, the moments of guilt were fleeting, and he could look back and almost smirk at himself. If Aslan asked if he felt forgiven now, he would respond with a resounding yes. He could even talk about it with only the slightest amount of guilt, he knew he was forgiven on all sides. Later when Eustace came to Narnia he wanted to tell him about what Aslan did for him. He felt that Eustace should know about Aslan's death and rising again and his own rebirth, so that Eustace could have the same joy. Edmund was at peace with himself. All thanks to Aslan's help.