His first thought of the day is always a variation of "Sue's side of the bed is cold. She must have gone to work early."
Then it comes back to him.
He never sets up a place too many at the table, but his grocery lists are still off. He has learned to avoid mirrors; from his rumpled socks to the irritated skin around his ring, everything in him sets up an inference chain that ends up in Sue's death.
Everything out of place in their home is also a clue, so he cleans up obsessively. He can't avoid thinking about her while he's doing it, but afterward he can be at home.
Sort of. He will try to open a file, work on a case, and a few minutes into it he will wonder half-thoughtfully about the silence, and then remember.
He tries to work, to live, to do the things he knows Sue would want him to, but he's too good at detecting odd things, and there is nothing odder in the world that Sue's absence.
Some nights he wonders if he will end up killing himself, and when, or if he will just crack under the pressure of his grief. He has seen some clues.