He places the other envelope on the desk, regards it for a moment, then sends Sherlock a carefully neutral text: ‘How long will you be?’
And then John’s just waiting, something he has a talent for. At home he smiled and did his homework while rows stormed over his head; on the Afghan steppe, he was the most professional, vigilant medic and diligent watch officer. Good boy John, always anticipating other people, whether they’re going to flounce off, bleed to death or fire rockets at him.
These past parallels with his current situation occur, and are dismissed. Ridiculous, to see necessary medication for his lover through the filter of his own weaknesses.