Dear Sammy,
I know you want to understand the way I'm feeling at the moment, but the truth is, that's it impossible for you to do so. As much as I want to get everything out in the open and be all "caring and sharing", it is not in my nature, as you are probably already aware. But either way I am going to use this opportunity to at least lessen the burden that I carry with me.
When you died, I felt as if I'd lost everything, I didn't really believe I had anyone else. You meant everything to me and I truly could not live without you. All of my life it has been my duty to watch out for you and make sure that you are safe. When Jake stabbed you, and you died in my arms, the empty feeling of failure overcame my body and mind. I had failed you and I had failed Dad. His last words to me were "Save Sammy", he had trusted me with this huge responsibility and I had let him down. When I saw a way to bring you back, I felt I had no choice but to take it, you're my brother, Sam. The only one I'll ever have and I would die for you. So this is what I pledged to do.
Now, having made that deal, I am scared and don't want to die, but I still have to, for you. You can't save me, and if it means you die then I don't want you to. You are my life and I'll love you til the day I die. I don't blame you at all, I chose to do this. I'm sure you are unable to understand my reasoning but please, when I die, do not give up fighting for the cause. That bitch Lilith deserves to die and it's my dying wish that she does so, in as much pain as possible. If you must, send her down to me and I'll deal with her myself, I'd quite like a little payback. And whatever you do, do not make a deal to bring me back.
Thank You So Much Sam, for all these years. I'm sorry to do this to you and leave you, but you are not alone. There is so much work to be done and since I'm not there to do it, I'm trusting it to you.
Dean