The Doctor heard her voice from outside the TARDIS, calling out for him, asking if she'd surprised him this time. He smiled, and restrained himself from running to the door, yanking it open and pulling her into his arms, not knowing what would be on the other side.
He did, however, step quickly and pull it open, using his hands to adjust his scarf instead of placing them on her. In her wedding dress. At what he thought was her wedding reception.
He spoke with the shield of wit and snark that he'd developed over the years, striding forward to meet Rory as Amy spoke the same way she always did, flirting with him and ignoring the person she was meant to be with. He brushed it off, pushing her in the opposite direction as he always did, doing the proper thing. He considered smacking himself in the head, if only to outwardly scold himself for daring to believe that he could have something decent happen to him for once.
He took his TARDIS away, giving himself a moment to assuage the turbulent emotions threatening to spill out of his mouth and eyes in a torrent that he would later add to his long list of regrets. Without thinking about the coordinates, he entered them, making sure not to change the time, only the place. He materialized in Amelia's backyard, and walked over to the wedding reception. Leadworth was so small, too small. He couldn't imagine his Amelia happy here.
Still, it was her choice, as always. So he would hide his feelings smile, dance at her wedding, and then, when she was distracted, he'd slip away and return to his TARDIS, his one constant companion in the past 800 or so years.
At least the TARDIS couldn't choose someone else; he was the last of the time lords, the last of the race with the knowledge to pilot her. Well, then again there was always River Song…