Needing Versus Wanting
Everyone had his own opinion on the matter, obviously.
Sergeant Donovan said that John needed to find a hobby, like fishing. But he didn't want to.
Lestrade said he needed Sherlock's help. John just thought he wanted to make sure that Sherlock was alright just as much.
Mycroft allegedly wanted his brother's help. Not that he couldn't find out things on his own, he needed to keep Sherlock safe and busy (and therefore happy).
John said he wanted to be away from the horrors of the wars, and death. What he needed were adventures and the adrenaline rushes that Sherlock could get them both.
Sherlock tried to convince himself he didn't need sex, that he didn't want John that badly, hoping against hope to outrun his own logic.
John made him admit that for once, for him, needing and wanting coincided. And converged in him.
So later, when Sherlock was begging him, "More... need more!" and clawing his back in rapture, John did not try to correct him but gave him what he wanted in that moment.
Like he always did.