Sometimes he just sits there and wonders, Where did it go wrong? Of course he knows. But asking the question aloud shows that he hasn’t given up yet, that he still wants answers. He needs them. Just as badly as he needs her.
He never expected Molly Hooper to become so much to him, but then again, she’s always been like that - surprising, being invisible until you realise how great and beautiful and intelligent and patient and thoughtful and utterly perfect she is. She’s been his everything for months after the divorce - and if he wants to be honest with himself, even before that. Two lonely souls met and collide and made sparks. That’s the way it’s always been. Just look at John and Sherlock.
Sherlock… He’s what went wrong, of course. Jumping off a roof, confessing he was a fraud. Greg’s work going to waste, his reputation thrown to the wind. And Molly… Molly who came to him and said, I’m sorry, Greg. I can’t keep seeing you.
He just can’t figure it out. Sherlock is dead, they need to be there for each other, for John, even for Mycroft, somehow, because he is more affected than he would ever admit it. But she just left, saying I hope someday you’ll understand. I hope you’ll be able to forgive me.
But what is there to understand, really, apart from the fact that the woman he loves doesn’t want to see him ever again?