John Watson had been all-too-keenly aware of the speculation surrounding his arrival. His arrival into the mad, crazy jumbled up world which was the life of Sherlock Holmes. People had talked. Sherlock was right; it was all they ever seemed to do. Was he Sherlock's acquaintance, colleague, social worker or perhaps even Sherlock's friend? The mere suggestion of that latter seemed to be impossible, apparently, if one listened to the gossip. John Watson was not a fool. He had heard the speculation, with people wondering how somebody like him could ever possibly be friends with somebody like Sherlock?
The simple truth of it was that it was irrelevant what everybody else thought. The only person whose opinion mattered was Sherlock's, and Sherlock had said that they were friends. After all, it was Sherlock that John had either been sent to, or chosen to, help, not anybody else.
Truth be told, John himself didn't quite know how it had happened. One minute, he had been treating a fellow soldier on the battlefield, and the next minute he himself had been on the floor, writhing in agony after a stray bullet had torn through his shoulder. All of a sudden, even as he lay there on the floor, all of the pain had seemed to drain away in an instant. John remembered light; an overwhelming, bright, overexposing light which illuminated everything too intensely. He had a vague recollection of thinking how ironic it was that people said 'whatever you do, don't go towards the light', when all he now felt was an overwhelming compulsion to do so. And so he did.
John moved towards the light, and this was the last thing that he remembered before 'waking up' and finding himself in the middle of an appointment with a therapist. A therapist who could tell him everything that he already remembered - he already knew that he had been a soldier, it was not something he could easily forget - but could apparently tell him nothing about what he could not remember.
All John had been left knowing was that whatever it was that had happened to him during the time in which the light had consumed him, it had left a lasting impression. He hadn't lied to his therapist when he had said "nothing happens to me." What he had - rather conveniently, he thought - failed to mention to her was the fact that he could make things happen, either to himself or to other people.
And that was what John had done. Bumping into Mike Stamford had honestly been a genuine coincidence, but when John's old friend had just happened to mention that he knew of somebody who was in need, and was feeling the same despair as John had expressed through his "who'd want me as a flatmate?" comment, John could not deny that he had been intrigued. As such, he may have just happened to give Mike a nudge in the right direction, asking for a quick tour of the Barts that they had shared during their university days for 'nostalgic reasons', especially since he was now seemingly stuck with a walking stick, and a limp to match.
Just as John had thought, Mike's associate was exactly where Mike had left him earlier in the day. The associate had introduced himself as Sherlock Holmes, and then proceeded to do a mental 'reading' of who John himself was. This was all fine though, because it gave John chance to do a little 'people-reading' of his own. It was clear to anybody who bothered to look that that, right here in front of him, was a man who needed somebody. Needed somebody constantly, but was just too stubborn to admit it. That suited John just fine, because that was exactly what he needed too. He needed somebody to help, to make things happen for, and here was the perfect person just in front of him.
John knew that, on his own, Sherlock Holmes would be a formidable opponent for anybody to face. However, John's new insight could also tell that, if given a helping hand in the right direction, Sherlock Holmes would be unbeatable, and more-than-a-match for anybody that came along and tried to interfere, or challenge, or destroy.
Put simply, John could tell now that Sherlock needed Five Lessons. If John could manage to teach him these Five Lessons, then Sherlock Holmes would not only be a great man: he would be something else entirely.
The First Lesson was for Sherlock 'to believe'. Sherlock already believed in his own capabilities, but what he craved was for somebody else to believe in them too. He also needed to be able to come to terms with, and believe, the fact that somebody might willingly want to believe in him, without being coerced into doing, being guilt-tricked into it, or doing it because they pitied the lonely man.
John could, and did, help Sherlock with this. He turned up at the flat viewing in Baker Street, even though it had been obvious that Sherlock had never expected him to show. He told Sherlock, truthfully, that he was "amazing", even though they were both perfectly aware of the response that Sherlock's deductions were usually met with. And slowly, piece by piece, Sherlock started to believe. Started to believe that others could see in him what he had been able to see for years. Started to believe that not everybody would shun him, or be terrified by him, or threatened by his intelligence. Sherlock learned that some people could just be accepting, and this was all that he needed to know. With one Lesson learned, the tremor in John's hand had disappeared.
The Second Lesson was for Sherlock 'to trust'. Of course, it had been inevitable that somebody would have taken tremendous issue with the fact that John had suddenly materialised in Sherlock's life. This 'somebody' just happened to be Sherlock's own rather overprotective brother, Mycroft. As expected, Mycroft had attempted to bribe him into spying on Sherlock, and - as was also expected - John had not been in the slightest bit tempted by the offer. When he had visited Sherlock in his flat a short time later, Sherlock had not trusted John enough to be able to safely assume or deduce that John would refuse the money. Sherlock had physically asked him whether he had done so, and then simply accepted the answer.
For Sherlock to be able to trust somebody else completely came with a little more time, when John did not hesitate to kill the cab driver who was threatening to kill Sherlock himself. Sherlock had deduced this fact without having to ask for verbal clarification from John first, and had trusted him ever since. Nobody had ever killed somebody like that for Sherlock before. Sherlock now trusted that somebody wanted to be his friend, not despite of who he was, but because of it. It was somewhere in between these two stages that John's limp disappeared, as the Lesson was learned.
Sherlock's Third Lesson was 'to learn to work together'. Now that the basic ability to form genuine connections with people - and to believe that they were being created for no other purpose than the fact that both parties wanted to do so - had been achieved, the third Lesson that John wished to teach Sherlock was the ability to work with somebody else. John needed to get Sherlock to understand that needing to work together with somebody else was not a weakness; instead, it was a strength. All through the case of 'The Blink Banker', Sherlock had worked alone, with John tagging along like an adoring puppy. John himself had chided Sherlock about it, impersonating Sherlock by stating that "'I'm Sherlock Holmes, and I always work alone because no-one else can compete with my massive intellect!"
However, this had gradually changed, and by the time they reached the beginning of Sherlock's 'Great Game', John was Sherlock's assistant, with Sherlock trusting him to do his own enquiries on cases, even ones as high-security as Mycroft's 'Andrew West and the missing memory stick' case. Also, Sherlock now allowed himself to admit to John in private that "he'd be lost without his blogger", with the aforementioned 'blogger' being another one of the roles which John had assumed. With the Third Lesson learned, John's temper became calmer and less confrontational, as he no longer needed to push Sherlock so hard into doing some of the things that they had been working together to achieve.
The Fourth Lesson learned was for Sherlock 'to make a leap of faith'. At the beginning of the 'Great Game', Sherlock had his first notable chance to make this leap of faith. Unfortunately, it hadn't been in a situation that John had devised. Rather, it had been one which he had been dragged in to. At the pool, John had been strapped to an explosive device, and yet all he could think about was whether or not Sherlock would fall for the ruse; the ruse that it was actually John who was Moriarty, and not the mad man named 'Jim from IT'. There had only been a moment of doubt in Sherlock's mind, a moment when Sherlock thought that John had been deceiving him about his identity all along. It had disappeared almost as quickly as it came - once Sherlock's logical mind had taken over from the shell-shocked emotional one which the detective tried so hard to pretend that he didn't have - but it was still there, and that was something that John resolved to change.
The Lesson was finally learned in a situation that had been even more dramatic than the first, something which - at the time - John found hard to believe. Sherlock had learned to take a leap of faith when he had, at last, physically had to. Sherlock had been forced to put his faith into John, to trust that John would do everything that Sherlock asked of him, no matter how much the doctor didn't want to. John had told Sherlock previously that he believed in him completely, and that he knew that there was no way that Sherlock could be a fraud. It had been during the most intense test of their friendship so far, and yet Sherlock's leap of faith was to believe that John meant what he said, and to devise a plan around this accordingly.
Sherlock's leap of faith was to protect John by 'sacrificing himself', and to come back to John after his work was done, even though he had computed that there was the possibility that John might deem Sherlock's actions to be unforgivable, leading to John rejecting Sherlock. Rejection had been one of the things that Sherlock had feared from John most in the early stages of their friendship, and now Sherlock had to have faith that it would not happen now. After this Lesson was learned, John's limp did not come back. John thought it had been healed by Sherlock's actions, but he later came to realise that it did not come back because Sherlock wasn't actually dead, and his trust in both himself and John had not been misplaced, because his plan had worked. Therefore, the leap of faith was also revealed to include Sherlock needing to have faith in himself, and not just having faith in John, or John having faith in himself.
The Fifth and Final Lesson occurred upon Sherlock's return. John recalled that Lestrade had once said: "Sherlock Holmes is a great man, and one day, if we're very very lucky, he might even be a good one." This turned out to be the Fifth Lesson: to be good. After completing his task and destroying Moriarty's criminal network, Sherlock could have chosen not to return. Legally, he was dead, and he was dead in the eyes of everybody he knew, or of everybody that knew of him. He had no logical reason to return. And yet he did, because he saw how heavily the loss which he had forced upon his friends, and those who relied on him for help, weighed upon them. Even though he knew he might be met with rejection and ridicule, he returned to ease the suffering of people who cared about him. It wasn't easy, but it was the right thing to do. It was also something that Sherlock would never have done, or even considered doing, before meeting John, and so Sherlock's selfless act here meant John's Fifth Lesson for Sherlock was complete.
Sherlock Holmes was now a good man.