He breaks, tired all of a sudden of pretending that everything's still fine-and-dandy when it is obvious even to him that he is simply not coping, shortly after making sure Donna is safe back at her parents' house; for what seems like for ever (it's not,ofcourse, but it bloody well feels like it, from his point of view) he is a total, utter mess and the tears flow faster and more thickly than he would have thought credible fewer than three regenerations ago.
(The fact that, three regenerations ago, this would never have been an issue is something he refuses to contemplate; it's just another self-fulfilling argument and another one of those is the last thing he needs at the minute.)
Past the disbelieving stage more quickly than he wants to have been, he shouts a lot at this point – well, shouting is the wrong word; he screams at the TARDIS, at the universe, at anyone or anything unfortunate enough to be within hearing range – and lashes out with slaps and kicks and punches at whichever parts of the TARDIS he can reach, as if blaming the ship for his losing Rose.
The part of his mind that's still rational knows that it isn't the TARDIS' fault, of course it isn't, but at the moment he is far from rational and he is so far from caring about that fact that it almost surprises him to think so.
It's a long, long time before he feels sane enough, or good enough about himself, to want to leave the time vortex. Even longer before he can even let himself think of going anywhere near Earth. At the moment, it's anathema to him – he wants no reminder of what it is he's lost, and he knows that that's all he'd be getting if he went back there any time soon. So he roams time and space, a little like hehad done straight after the Time War when he was alone (really alone) for the first time in all his lives.
He knows that the destruction of his planet and his people is supposed to be a grief that's unsurpassable; he wishes someone would tell this to his brain, his soul, his hearts. The pain he's suffered since that god-forsaken Norwegian beach is stronger than anything he can remember; and he loads this guilt on to the growing pile – that a slip of a girl has meant more to him in the short time he was with her than people he's known for lifetimes.
And it's while he's in this happy frame of mind that Martha Jones runs into him at Royal Hope Hospital.