OK on rewatch I am wondering if he’s not talking about not knowing how to diffuse the bomb. I’m thinking he doesn’t know how to navigate his mind palace. John forces him to and he yells he can’t and then he truly looks panicked and John looks disgusted. He searches for a switch… says “turn that off” and then he does. Then he says “I’m sorry. I can’t, I can’t do it, John. I don’t know how” I think Sherlock had indeed been damaged and I think maybe he thinks that is all he’s got to offer?
This could be prime not talking about what you think he’s talking about Private Life of SH Gatiss version of “Am I being presumptuous? There have been women in your life haven’t there?” “Yes”
He winces each time he goes there. He avoids it and is defensive in the carriage. I think he was going to confess it and changed his mind by John’s reaction.
I think maybe he does find the switch the old fashioned way (searching) after the panic and laughs it off? Maybe?Clarification: I think this sounds a bit convoluted. What I mean is basically Sherlock’s Mind Palace is damaged. He considers telling John about this problem… and even starts to during the bomb scene. That’s what he’s really taking about here. But backs off because of John’s reaction. Maybe?