There is nothing that is going to help him now, he knows this for a fact. Donna casually dropped in to the TARDIS after he was mourning for Rose, and that helped him keep moving until he properly recovered. This time, he has no one. Maybe someone dosed in huon particles will get zapped into the TARDIS, but if they did, he'd look at them apathetically and tell them that there's nothing he can do.
(Then he'd drop them back off on Earth somewhere, and bolt back into outer space and loneliness like he was on fire.)
He hangs out above Earth for a while, and sits like Brian once did, with a cup of tea and his feet dangling out in to open space. He wonders what Amy and Rory did with their lives – did they ever manage to have the child they so desired? Were they happy in the end?
He looks at the afterword sometimes, and wonders if it's true at all.
He furtively drops back in on Donna, and Martha and Mickey, who are all living fairly normal and productive lives, and breathes a quiet sigh of relief that he hasn't totally and completely screwed them up. (Well, maybe he did, and it weighs on his conscience, but sometimes he's got so much weighing on him that it all blends in to one massive monolithic bad deed that threatens to drive him insane.)
He can't stop thinking about Amy, and her face, contorted with pain when she made the decision to get sent back with Rory. In his mind, there's a little bit of hesitation in her step and her voice as she turned to say goodbye to him that one last time, as if she wasn't totally sure whether she was going back to her husband or travelling with him. (The only place for Amy Pond in his mind is in the TARDIS with him, but clearly, he's quite wrong about that.)
The better angel of his nature tells him that she loved him, yes, but not in the same way that she loved Rory, and that's entirely and totally okay. She made her decision, and he ought to be happy about that and continue with doing what he always does – saving the world.
He cannot convince himself of that, because in his heart, he's selfish. He wanted Amy for himself and only himself, despite the fact that it would never actually happen, because he loved her, loved her more than the husband who wanted to make her settle down, and who walked out on her when he discovered that she couldn't bear children. No, he could have shown her the stars and taken her anywhere and everywhere she wanted to go.
He walks past the room with the bunk beds and debates taking the whole set and chucking it in to a black hole. He is stuck at an existential crossroad (and this is why he needs to keep travelling and running) where some days, he feels like eradicating all reference to Amy from his life, and on others, he wants to preserve all of it as if there's a chance it could bring her back to life in some twisted way.
The other reason that he isn't travelling much is that the TARDIS is acting up. He's stuck hovering above earth, and also stuck in prehistoric times without the slightest clue as to how he got there. The continents are all stuck together, and when he watches superstorms erupt on Pangaea they match the ones within him.
He fiddles with everything that's wise for him to fiddle with, but she has firmly decided that they aren't going anywhere at all, and she's always decided that she has a mind of her own.
He kicks the console in frustration, and then jumps in the pool with all of his clothes on, hoping to drown, but he has become too human and pushes up from the bottom at the last minute. (Damn those survival instincts.) As he lays his clothes out to dry, he also realises that drowning himself wouldn't have done anything – he'd just regenerate, and leave another poor soul with all of his memories. That'd be incredibly and exceptionally cruel.
One day (well, it's day over the ocean, but night for whatever life's on Pangaea, or most of it) the TARDIS comes back to life in a rather spectacular fashion. She lurches hard to the left, almost so hard that he's thrown out (never sitting with his feet dangling out ever again, because now he knows that that can happen). Suddenly she starts flying through the years faster than he knew she ever could, which freaks him out immensely. He tries to fiddle with the switches and levers on the console, but to no avail – she is going where she wants to go, and that is going to be that. He decides that if he can't control where she's going to go, he might as well watch, so he peeks out the window and observes the continents split, and gets far too close to a massive asteroid that wipes out the dinosaurs (and the Silurians too, he realises with regret), and then sees a cloud of dust consume the earth and then disappear, and Africa separate from South America and the continents take their present order, and then after a bit where nothing really happens, the TARDIS starts going towards Earth at a frightening speed.
He is thrown off of his feet, and now he's just mad.
"Excuse me," he yells, "if you felt like not trying to kill me any more, that'd be wonderful!"
He manages to get up on his feet and sees them zip across Africa, and then north over Europe and finally back over Britain.
"Oh, don't take me to Leadworth, please don't," he shouts at the console. "I can't explain this to Brian, or Aunt Sharon, or anyone. Please, please don't."
He nearly takes one of the clock hands off Big Ben (again!) but the TARDIS presses on in a generally northward direction, he guesses.
Up until they're over Edinburgh, they maintain a decent altitude, but she stops with a lurch over a block of flats not far from the city centre.
"What are doing?" He yells at the console as he tries to get up. "You and I need to have a serious –"
She drops straight down, and owing to gravity, which is as heartless as ever, he is pressed against the floor. He prays that they don't hit someone's flat, because that's going to attract far more attention than he really needs.
"Is this how you're going to introduce me to a new companion?" He yells as they fall. "This, by the way, is totally the wrong way to go about it, if you were wondering!"
The TARDIS swerves, which he suspects is the only way they don't render an innocent citizen of the city of Edinburgh homeless, and then plops in to someone's flower bed.
He hits his head on the console during the fall, and when he regains consciousness, someone is banging on the TARDIS doors. He straightens his tie, stands up, and opens the door. He nearly faints again when he sees who's looking back at him.
"That's two back gardens of mine that you've ruined, Raggedy Man," Amy says with a smile. "You're going to have to come in for tea to make it up to me."