The nights are hardest.
Peter fills his days; in many ways his days are filled by fringe events, just as they ever were. Only that now he's on the outside in ways he never knew even back in the beginning. This Lincoln likes him and this Olivia tolerates him; this Walter is intrigued despite himself.
But at some point Peter has to close his eyes, and much as he wills his mind to go to rest, it doesn't -- well, it does; it turns to his Olivia. He sees her smile, the one that's just for him. Sometimes he still wakes with a start, shocked momentarily to find her body next to his missing: no warm weight, no familiar scent.
Sleep is always an even longer time coming, after that. Sometimes he wonders if he should get up again, altogether, and wander the city like the ghost he feels he is without her. Clichés are clichés for a reason.