I guess the time before losing consciousness with SN scares me. Not knowing how painful, miserable, SI kicking in, etc. I absolutely do not want to fail. This is the hardest decision to make.
I spent a lot of time researching the method, planning, and preparing. I did a journal on the forum about the planning and preparation. I came to the conclusion that I am not able to easily tolerate some of the symptoms I'm certain I'll have, so it is my backup method. I have others, and will only do SN if I fail.
I've also thought a lot about SI. I've come to the conclusion that it's a matter of circumstance. For instance, I am terrified of heights and can't jump, but if I were near a cliff and bunch of terrorists were heading toward me and I knew they would torture me if they caught me, I would overcome the SI and jump, because jumping would be survival. For me, there's a message in SI: "I just can't."
For now, when I consider SN, I just can't. If the other methods fail, then I will have to adjust my thinking, so that I can. I need to be able to ride out those many minutes of discomfort like terrorists are and I need to get it over with before they get to me. I need the determination. I'm not sure yet how I'll accomplish that, but I know that I can, it's just going to take a lot of meditation and mental preparation. I have to be 100% confident and certain, then the symptoms won't matter so much. I need to be in the mindset that I can, and that I will.