Sherlock tilts his head, eyes narrowing slightly by the way John says 'client.' He's upset, Sherlock decides, though he can't fathom why that would upset him. In his mind, it's the only natural thing for him to have been doing outside of being at Scotland Yard, Bart's, or visiting a crime scene. It's simply what he does. It's nearly the only thing he does when he's not sitting around the flat either working on experiments or complaining noisily about boredom.

He simply stands back as John tries to pull himself up from the sofa. He feels that if John falls flat on his face, it might help to sober him up some. He starts to reach for John when he sways too far to the left, but his hand doesn't reach its destination before his friend somehow rights himself.

So that's what this is about.

"As you can see, I'm perfectly sound," Sherlock tells him as he turns to face his retreating flatmate. He doesn't mind so much being pushed aside like that, but he does mind John wanting to go upstairs when he's clearly too drunk to be left alone. He'd still go up periodically through the next few hours to make sure John's lying with his face to the side, but it would be much easier to do it if John were to just stay on the sofa.