The Stone.
Days and endless nights spent obsessing over it meant that Harry had figured out pretty much exactly where the Stone would be if he only went to look. The Stone. It itched on the edge of his mind, never ending, whispered in his ear, the ultimate temptation. His lifelong obsession finally made possible, to see his mum and dad, to hear their voices, to speak to them. Why was it so wrong to give in? Why could he not have this one happiness? Hadn't he earned it yet? Was there more he needed to do?
He was disconnected from the happiness that surrounded him. The celebrations faded into the background, the grief for those fallen just a passing murmur. The parties and memorial services he attended blurred into one. Even his friend's attempts to talk to him, Ginny's impassioned pleas fell on deaf ears. He could talk, he could kiss, he held Ginny in his arms, sometimes even laughed, but all of it felt unreal. The one thing occupying his thoughts, pushing all others into insignificance was the Stone. The ghostly figures he had seen, that he had even talked to, were calling to him, calling him home.
And yet he did not go to it. He knew each day it would slowly be buried, that it would be harder to find each day, each hour he delayed. He knew one day it would be impossible to find, but the fairytale and Dumbledore's words, both when he himself was dead and when he encountered the Mirror of Erised in his First Year, held him back. He would not disturb those who were at peace and he would not give himself over to hopeless dreams.
It was the middle of the night when he gave in. The temptation was always worse during the night with no one to distract him, no one to show him the pleasure of living rather than the obsession of death. He wandered the forest for hours before he found the place of his sacrifice. He spotted the Stone immediately, as if it were calling to him. He rushed over, almost fell down beside it, clutching it in his hand, but he did not call them to him, not yet.
"If you want," he murmured, "I'll leave this stone here and never come back again. You don't have to come if you don't want to," there was an answering murmur from the stone, and a strange feeling, almost as if arms gathered him in a comforting embrace.
"One day," they answered, and he could not distinguish between the voices, between his mum, dad, Sirius, Remus or Dumbledore, "one day we will call you to us once more, but for now Harry, for now you need to forget your dreams of death and remember to live. You have so much to live for, your friends, your love, your Ginny. You can change the world, Harry. You could become the greatest Auror there has ever been, but you need to move on from the past, move on from us. Do not mistake us, there is nothing we want more than to return to you, but the dead are not meant to exist among the living. Live, Harry, live and be happy. We will see you again when it is time." Harry moved his head away from the Stone, tears on his face. He had known all this time what the Stone was, what he had to do, but had not been able to accept the truth. Now he had no choice but to give up his dreams.
Harry spent a long time burying the Stone, then turned and walked away. The first step was almost impossible, but they became easier. He did not recover from his obsession instantly, but it was if he had awoken from a dream and he now knew where he was going and what to do.
Harry never forgot the Stone, just as he had never forgotten the Mirror and he still longed for that one last glimpse but he knew that if he ever gave into his obsession he might never recover.