John,
I'm so sorry. I wanted to tell you so badly that I wasn't leaving you. I didn't want to leave, but I didn't have a choice, it was that or I had to live without you. I could never live without you John, I would be lost. You're an exception to my rule, you're my friend. I couldn't bear it without you. I'd rather die than be without you, so that's what I did, I died.
I saw you the other day, you looked lost. I wanted to come over and tell you that you'll be ok, but I can't. You're not safe. You think you're the only one in pain; I'm the one who has to deal with the fact that I can't come to you and tell you it will be alright and that you're not alone. I can't just go back to 221B and sit in my chair. I can't watch you make my coffee in the mornings as I like it.
Life is impossibly hard. That phone call was the hardest and worst thing I've ever had to do in my life. To know that I was destroying you, and Mrs Hudson and Lestrade. It was so hard. I don't know how I did it, will you ever forgive me for ripping your heart apart, demolishing any hopes for you to have a happy future. I saw you at my grave a few days ago, the way you broke down as you said that you wished I was alive. It's the hardest thing to keep yourself from being able to see the one you love, to not even be able to tell them that it's ok, to hug them and dry their tears when they're broken.
You've changed my life John, and now I've changed yours for worse. I will fix you; I will be there for you. I'm always there for you; I'm here for you now. Even though you don't know it. I'll help you get back up.
I love you.
Sherlock.