Letās just think about what Mycroft said:
āYouāre not haunted by the war, Dr. Watson.ā Wrong. We see John wake up shaking from what is obviously a nightmare, not wartime macho fighting nostalgia. He looks shattered when he wakes up. Haunted by the war? Yes indeed.
āYou miss it.ā Sort of? I think John misses being Army Doctor John Watson. He misses that part of his identity, and the feeling of utility that goes with it. I donāt think he misses the war itself. He misses feeling like he can move around and help people and make things better. Because heās alone and jobless in London. Thatās why he snaps at Mike Stamford that heās ānot the John Watson you knew.ā Thatās why he doesnāt want to write in his blog until Sherlock. Because before Sherlock, all he can say is āNothing happens to me.ā
John chases after danger, and Sherlock gives him that. And honestly, I think he needs the danger not because he misses the war but because the shock of his transition back to civilian life has numbed him and he just wants to feel something, anything. He needs the adrenaline. John chases after Sherlock because there is suddenly this brilliant man doing exciting things and solving crimes and heās right there and he wants John to join him. Even if he isnāt really helping solve cases, even if heās just a substitute for Sherlock talking to that fucking skull, Sherlock makes John feel useful again.
And, with all that Sherlock has given and how much John comes to love him and what we now know about how John handles stress and loss (at least in relation to the war) and all the progress that he (presumably) makes with his PTSD as the series progresses, just imagine how much The Fall sets all that back.
John goes from āNothing happens to meā at the beginning of the series to having nothing happen to him at the end of series two. āNothing happensā in the sense that he is not injured or killed.
Not injured or killed, but you can bet your ass heās hurt. Broken, even.