I really, really, really love JLM’s Sherlock, he is like a really precocious child with no impulse control. He isn’t callous and I don’t think he intended to hurt Joan in the opera ticket scene but he isn’t able to control himself when he gets overwhelmed by his feelings - which i think is what lead to his car crash temper tantrum and might be why such an intelligent man became an addict.  

I think he does need Joan. He needs someone there that can set boundaries and help him out when he gets himself arrested or insulting someone. And she needs him to give her an occupation she actually enjoys again and you can tell she gets a little kick out of his weirdness.

They are the perfect brotp.