Forget it, Sherlock keeps saying. As if that's something you just do, as if John actually cares to do that. He's not going to, and it's beginning to get on his nerves how Sherlock says to forget things and that it doesn't matter and. Whatever. Tries to deflect it all as unimportant when it isn't.

He frowns, shakes his head.

"I'm not... saying it's your fault, Sherlock. I get it. But I don't have to be happy about it just because of that. I can't be."

It's possible to understand and be unhappy at the same time, so he's going to be.