You could have used it.

[Sherlock won't bring those things to light. It would take the conversation into an area he's not comfortable with. Joan's done wonders to teach him how to be more human and to accept his flaws (read: emotions) as a part of himself. But, he'd just as soon not talk about them. So much easier to repress and deal with them all at once down the line.]

When I said I wished I had my violin, I meant presently. I would use it to put you back to sleep.