He didn't want to stop remembering.
He was probably the only one who had believed in Sherlock when he threw himself off that building, and he had to keep that legacy alive.
He was going to prove Sherlock was innocent.
As much as it hurt to be without him even after three years, as much as he missed him like he never missed anyone before, he still had to go on, he had to be strong.
It was one thing telling himself that, but it was quite another to actually wake up in the morning.
It hurt.
It physically hurt.
Because his life was boring.
Even when he helped Lestrade, it just wasn't the same.
It wasn't the work he missed, it was the person of Sherlock Holmes.
He missed taking care of Sherlock.
He missed all the things he learned from him.
He missed how they laughed together, his humor, his brilliancy.
He knew Sherlock hadn't killed himself.
Or better.
He knew he had done it to protect them.
It was obvious.
Or maybe John just wanted to believe that Sherlock would never up and leave him like that.
Not when John trusted him over anything and anyone.
So every day was leading into the next, his progresses in the case against Moriarty were slow and far apart, and his work took a lot of time from him.
He didn't date any more.
He felt he couldn't love anyone.
His heart had been torn apart, broken, he couldn't possibly connect with anyone.
He was perfectly content. Lonely.
As long as he could sit in his chair, look at the one that was Sherlock's.
And remember.
It was three years today.