I'm not particularly worried. In addition to what's going through my mind when I'm practicing and what's been in my mind when I was having a perceived near death experience, I've gotten a fill of my thoughts and they're nothing scary.
When I've practiced finding my carotid sweet spot in a noose (to be clear, by practice I mean 'trying to find it and if I find it then I'm ending it right then and there') the last things I always say are some silly phrase ("nothing could be grander than to be in Louisiana" was the one I last remember using) and my thoughts are always about focus and technique. On the rare instances I've genuinely felt close to death it's always been very peaceful, almost like nirvana. I remember when I was 4 I had one experience that legitimately made me feel like I was about to die and I remember the total peace of mind I felt, and sheer acceptance of what was going to happen. I was actually disappointed when I survived that one because I was so ready for it and it just didn't happen.
I think that ultimately despite how painful your attempt is, when you're finally on that precipice between life and death the only possible thing that's going to happen is that you will feel that peace. I don't really believe there's an afterlife and that peace, as beautiful as it is, is all we're going to get, and our mind knows it, so it's going to give us it if it feels that there's no chance of survival. Everything becomes okay. It's like the silver lakes on Saturn if you get deep enough into the gas giant. It's just a matter of how far you're willing to go to get there, and just how painful that journey might be.