To me, death in itself could never be terrifying as I believe death to just be the absence of everything, the only relief for me lies in the thought of being unable to suffer and being unable to be tormented by existence. What terrifies me instead is a suicide attempt failing and just leading to more suffering, and of course there's the fact that the SI can kick in if one is trying to attempt ctb. But I do think it's true that the terrors of existing can make someone more determined to try and attempt, that's how I think that people manage to jump, they just get so desperate and determined.
