He was always cautious. He had to be, if he ever met up with himself something terrible would happen; the Time Lords of Old had always talked of it when he was young. So he was careful never to time jump too near to where he had ever been before. But this one time he had wanted to see something that occurred just a week after a visit he had make in his previous body.
The London fireworks on New Year's 2008. And he was meticulous, trying to get his coordinates just perfect as to avoid himself. But of course the TARDIS chose that moment to go haywire and miss the time by oh, about a week. Shit.
And he hit the time stream of London, December 27, 2007 where the most recent version of himself already existed. But there was no way he could jump the 4 days he needed without ripping a big gaping hole in the wibbly-wobbly, timey-wimey ball that was the Space Time Continuum. He thought he was clever enough to always be 2 steps ahead of himself so he waited it out.
So he stayed and watched himself. And dear Gallifrey was he gorgeous. All lean torso and long legs, big brown eyes and spiky brown hair. With the pinstripe suit and Converse trainers he was beautiful as he traipsed through the city, completely unaware of the danger that was himself that lay, watching him.
But he let his guard down at one point just to drink at his favorite pub in 21st century England, King Ianto's Coffee Club. As he stared at his scotch, one hand in his pocket absentmindedly fingering his sonic screwdriver he missed someone sitting down next to him. And when he looked up and noticed that it was himself and his old form noticed him he braced himself for the worst.
But nothing happened. Nothing exploded or imploded or disintegrated or ANYTHING. So he took his chances and flirted with himself, buying his previous form a drink and spinning made-up yarns of his international travels as to not give away his identity.
And as 2007 became 2008 he kissed himself, his younger, gorgeous self. And all was good in their world as they clasped each others hands and watched the fireworks. And later as they got more intimate everything was perfect down to falling asleep in each others arms. And maybe, just maybe he could be his own companion and keep himself sane and loved…
And that's exactly what he did.