This is so… intimate.
Just imagine that nothing had happened before this - nothing about the dead wife or the feeling of fault; that Sherlock didn’t stuff himself with drugs and wasn’t hurt by a very close person; that both of these are not broken anymore.
Imagine them having a little chat about some trivial everyday things, and then John saying: “I wish you knew how much I love you. My love for you is so strong that may even kill me one day. And.. I can’t help it, so I feel scared because of it.”
And Sherlock answering: “I..I know what you’re feeling. It’s okay, John. We will dance together through this storm”. Then hugging him with his hands slightly shaking. Just.. just too many feelings.