Aching with pain, Jack grabbed the nearest bamboo tree and collapsed onto the ground. He lay on his back, barely able to move. There was a rustling in the trees. He looked to his left, and saw Vincent sniffing around. He smiled as he realized the irony of it all - he was dying on the same spot he had woken up on that fateful day - 22 September 2004, the day his life changed forever. Vincent lay down next to Jack, who was grateful that he wasn't dying alone.
As his life ebbed away, Jack looked up at the sky, remembering all that had happened over the last 3 years. It had been the most significant thing ever to happen to him, even more than graduating UCLA, marrying Sarah or working with his father. The Island had changed Jack in ways he couldn't describe. Despite how much he had hated the place previously, Jack knew now that John Locke had been right. The Island was a magical, special place. Jack's only regret was not telling him that while he had been alive.
A smile spread across his face as, in the sky above him, the Ajira plane flew away from the Island forever. The most broken thing in his life, he had fixed. A twinge of sadness hit his heart as he thought of Kate, on the plane home, off the Island forever. Although they couldn't spend the rest of their lives together, Jack knew Kate would be happy. She had Aaron, Claire and Sawyer; they would be happy. They could live an apple pie life, and it was because of Jack's sacrifice.
Weakly, Jack closed his eyes as the last of his life slipped away. His friends were safe, the Island was protected. Everything was okay. He was done.