The first time you see it, it can hit you really hard, especially since Sherlock is on a total roll and John delivers the line “please God, let me live” in a way where you can be forgiven for not being sure if it’s serious or snark. It apparently has the same effect on Sherlock, as well.
We never do get any details on how Captain John Watson of the Fifth Northumberland Fusiliers was wounded in action. But from this exchange alone, it’s clear the situation was extremely serious. He was badly wounded, nearly died, and developed PTSD- Sherlock had himself earlier pointed out that the original circumstances of John’s injury must have been ‘traumatic’, and he meant emotionally traumatic, not just violent and painful. The blunt earnestness of John’s response even trips up Sherlock for a second or two, and he’s just been ranting and raving about not understanding why a woman would care about her stillborn baby after fourteen years. This also works as a tearjerker in hindsight if you recall ‘Please God, let me live’ whenever John is genuinely in physical danger elsewhere in the series.
Pretty much everyone in the room agrees that in your last moments, you would think about the people you love the most. John apparently had no one to think about when he was close to dying. He really must have been lonely even before he returned from Afghanistan.
I hate you for making this post because it’s the best I’ve read on this subject and it hurts.