Empty.
The flat wasn't empty. Oh, how John would rather it had been empty. He would have rather missed the sight of the man's clutter; he would have rather yearned for his scent on a random article of clothing; he would have begged for the touch of the dressing gown so frequently used for a good strop. Empty, empty was good; the world was empty of the man. Could the flat, could John not be as well?
Dull.
The world was so very, intensely dull. John wished it had never been pointed out. Of course, he had always known how stagnant moments could be boring, but never Before had he been so consciously aware of how horrid everyday conversation with a person could be.
"Well OBVIOUSLY you have the flu, Mr. Smith. All the facts point to that inevitable conclusion; you bore me. Can't you go away? Honestly, John, it's tedious."
Hearing his voice, that wasn't tedious. And yet, John wished it were.
Sentiment.
A chemical defect found on the losing side. All John did was lose anymore. He was dying, he could feel it. Everyday was another step closure to that inevitable conclusion. His body was shutting down; his mind was going. He had lost the will to live when his Heart broke, shattered on the pavement.
He followed the man everywhere, this journey included.
They say John Watson died of a broken heart. They say you couldn't blame him; only half of him was present for the past two years. He was practically inhuman for all the caring he did, all the compassion he had. His zest for life was gone. He tried, they know he tried, so although tears were shed at the ceremony, the little old lady, who was Not His Housekeeper, thank you very much, the Detective Inspector whose guilt was nearly too much to bear, and the British Government, forever The Ice Man, never begrudged him. The papers would romanticize his death, proclaiming he held his beloved's clothes on his lap as he pulled the trigger. Gruesome or no, they ate up the Shakespearean story, and tabloids sold, once more talking of the Fraud Detective and Confirmed Bachelor.
There was nothing romantic about coming home to find the body of the person you love wearing your clothing because they suspect that you are gone forever, were in fact presented with evidence to back this up. It's not beautifully tragic, it's just tragic. It's pain and rage and hate and guilt and love and sorrow and regret and death all in one. It is an in between state between Life and No More that no words or paintings can accurately describe. But The Man experiences them nonetheless; and it destroys what little of him is left. And there is nothing.
John Watson was a man who killed himself because he was too full.
Sherlock Holmes was a man who came back from the dead because he was too empty.
In the end, John was full of metal, and Sherlock had less than nothing.
So if the man who was already dead followed the man who wasn't supposed to be, what was it to deduce what happened and put him in the box underground? It was a vicious cycle, love and life and loss. But as the famous saying says: So it goes.