He knew it was going to happen. It was an undeniable fact of his existence. There was no stopping it.
The Doctor ran his fingers over a face that felt foreign to a pair of hands that had just been born into the world. Everything was different, resembling nothing of the past. That's how it always was.
His hair - which now held streaks of grey - was puffy in such a ridiculous manner. Well, ridiculous to him. He knew he'd get used to it, but for now he would be against everything for as long as he could manage. Eventually, his thin wall of rebellion would crumble. There would be nothing left of his past - nothing left of his old self.
The Doctor hadn't realized what he was doing until he felt his machine give a whirr, signaling that it was taking off once again. Even the sound that the TARDIS made sounded odd in his ears. It felt so wrong. So terribly wrong.
A sharp jolt was sent through the man's body as his blue box landed. He hadn't the slightest clue of where his machine had brought him. There was no way of telling unless he went outside.
He walked over to the doorway. His hand reached for the handle, but hesitated only inches away from the curved metal. The Doctor pressed his forehead against the white door, staring down at his feet as he fought a heavy feeling that washed over him. Everything felt surreal. He wanted this all to be a dream - perhaps a nightmare - but as the man reached for the icy metal of the door handle, he knew that this was all painfully real.
The Doctor swung the doors open, a motion that now felt empty and pointless. He peered out to wherever the TARDIS had taken him. His eyes narrowed as he looked around, spotting a familiar house surrounded by an overgrown garden. A small bench rested in the front yard, seating a young girl with fiery hair holding a stuffed suitcase across her lap. The Doctor watched in silence. A hint of sadness flickered in his eyes - which still held the many years that shone through his newly-colored orbs. He stood there until sleep washed over the girl and an old blue box materialized out of thin air.
A face peered out, but The Doctor quickly looked away. He disappeared back into his police box, carefully clicking the door shut behind him. The Doctor walked over to the main console that was placed at the center of the room. He began the process again, pulling a small lever and pressing a group of buttons in order to get the TARDIS in motion. This time, he knew where he was heading, and it made both of his hearts sink in his chest.
The Doctor could feel his throat constrict as he opened the doors once more, this time with a purpose. His eyes - glassy and clouded with a mass of emotion - slowly looked around as he gradually leaned his body out of the entrance.
He watched as a face that was no longer his chatted with a girl who was no longer his. Her silky brown hair wavered slightly in the breeze as she sat in an open meadow beside a man with a rather prominent chin. His green eyes lit up with happiness as a cheeky grin tugged at the corners of his mouth. The man's floppy brown hair was something The Doctor longed for. Had he always been so happy around his little Impossible Girl? Was that dress of her's always so short?
The Doctor's view became blurred, as if he was looking through water. Tears stung his eyes, threatening to spill down his cheeks. He could see nothing, but the laughter in his ears was clear as the cloudless blue sky that hung overhead. He didn't need his sight in order to see what was going on. The memory played like a movie in his head - only he wasn't a spectator in his mind.
Suddenly, the laughter paused. The Doctor dabbed at his eyes, trying to make out the couple before him. He didn't remember this part of the memory. The man with floppy hair cleared his throat, taking the woman's hands in his as he stared directly into her hazel eyes. Everything around them seemed to stop.
"We all change. When you think about it, we're all different people all through our lives," the man started, never breaking eye contact with his companion. "and that's okay. That's good. You gotta keep moving, so long as you remember all the people that you used to be."
The tears rolled freely down his cheeks, staining the sides of his face with warm, salty streaks. He closed the door behind him and pressed his back against the wood. The Doctor held his face in his hands. No sobs came. He cried in silence, mourning for the man he once was.
If only Clara had known what those words meant.