There’s no real reason why you decided to write a second-person narrative. It just came to be that the idea you had, and the story you wanted to tell, needed to be told in the second person. That’s fine. It happens.
But then what do you do? How do you go about addressing the story to someone imaginary? Indeed, are you even writing to that person? It’s not simply a case of changing he or she or I to you, not at all – the work needs to be created with that specific addressee at the forefront of your mind, the focus of all the words and phrases and sentences. And who is this ‘you’, anyway? Are you writing to the character, whomever that may be, or are you talking directly to the reader, whether real or imagined, an individual or a collective entity?
There are things to consider, then. There’s the narrative voice, the pace, the extra dimensions of invasion or a skulking, insidious engagement with what might be private and intimate. There’s the locus and focus and hocus pocus of your point of view, hiding somewhere between over the shoulder and inside the brain, both limited and wide, both homo- and heterodiegetic, depending on the moment.
And there might be other choices, if you want to make them: you can step into and out of the story, commenting as much as you direct; you can infiltrate the most interesting corners of your character’s psyche and see how they react to what goes on around them; you can relate their perception to your own, or vice versa, stealing from them or yourself to fuel emotion; you can project yourself into their stories, responding, interpreting, recreating.
So many considerations to follow that first one. You chose to write a second-person narrative, to tell a story in that particularly instrusive way, with all its inherent complications and technical difficulties. Tell me again, why did you do that?