I can chime in on this. Due to a workplace injury I have been forced to accept my mortality and it plagues my mind. I have lose a lot of function in both my arms where I can barely cut up my own food and it's heartbreaking. I constantly live in endless self regret and pity comparing myself to healthly people and how mindlessly I use to live life. When you add so much physical suffering that induces depression, accepting your mortality becomes much more peaceful in my opinion.
I think no regular person thinks of dying and the thought of nothingness is indeed scary. But as the thought of nothingness scares a lot of people, whatever is pushing you to CTb, you'll realizing that the agony of living hurts much more then feeling nothing. That decision of nothingness versus suffering however is a individual choice that has to be made by everyone.
The feeling of wishing you weren't being here due to mental health can easily be understandable to due a lot of people's circumstances which is why venting is important. However those who have truly lost hope (such as myself) the lost or your consciousness is what is viewed as peaceful. There's a reason why we say "rest in peace" because death is inevitable for everyone but it's the nothingness that is associated with peace, whether you die by CTB, freak accident or natural causes