The Doctor shifted uncomfortably on the bench. He felt vaguely foolish. One of the first things a semi-immortal time traveler learns is that it doesn't pay to dwell on the past, but here he was.
He didn't blame poor Jack, of course. He supposed that living sequentially through more than a century of history would tend to bring out a nostalgic longing for the future. So what was he doing here? He didn't even have Jack's excuse. He could, and should, move forward - always on to the next adventure. That was the way to stay sane.
He stood up, tucked the newspaper under his arm, and began a leisurely walk back to the Tardis. As he neared the alley where he'd left it, he heard a shout from a nearby street corner. The voice was that of a child, both familiar and strange.
"Hurry up! I'm going to be late!"
He leaned against the wall of an old building, obscuring part of his face with the newspaper as a boy and girl, both about 13 years old, rode toward him on their bicycles. He felt his hearts leap into his throat when he recognized the girl's red bike as the one he'd given her the year before, a gift from "Father Christmas". Her long, honey-blond hair fluttered madly behind her as she peddled.
The boy panted, "And whose fault is that? You're the one who had to stop and help a stray mongrel!"
"It was going to get itself run over if we didn't."
"Yeah, I suppose so..."
The conversation trailed off as the kids rounded the next corner. The Doctor watched after them for a few moments with a bemused expression.
Rose was Rose, long before she'd met him. For the first time since their forced separation, he truly believed that she would be fine without him. One way or another, she would have a fulfilling, adventure-filled, fantastic life.
Tossing the paper into a bin, he returned to the Tardis and disappeared with a whoosh.