I'm not as convinced of the 'peacefulness' of SN as a method so much anymore. I do understand though that it's a last resort for many people, and is by far preferable to 'other' means.
The thing that initially drew me to SN was that it was a purportedly 'reversible' method and was 'without permanent sequelae' in the event of failure. In my case I don't think that would apply (due to my pre-existing neuropathic medical conditions I'd likely develop post-hypoxic nerve damage). For healthy people that probably wouldn't be an issue, but we can't 100% know for sure.
Ultimately it is a poison and can cause distressing symptoms for up to 40 or so minutes (in some cases).
Also, since hospitals are so understaffed/overwhelmed by Covid right now, there's less of a likelihood that you'd survive the attempt even if you felt like backing out last minute & called for an ambulance. Some people have mentioned that the ER had to specially order methylene blue (the antidote) instead of just automatically having it 'on hand', as I'd originally assumed they would…
I'd just exercise extreme caution. Everyone metabolizes this stuff differently and realistically nobody knows for sure how they'll handle it until they take that leap.
Your hesitation/aversion is completely understandable and rational. Please don't beat yourself up over it! CTB isn't a decision to take lightly, ever.