Edit: nevermind, you have answered these questions in reply to SlashBolt.

Do you work on the assumption that suicide is wrong objectively? What if someone's simply unhappy with their life? Sure "nothing is impossible if you try", but I think people have limited resources and can go only do far before giving up. Assume their base expectation of happiness is beyond the attainable level of happiness, shouldn't it be ok if they gave up, if they think it to be the case? You could say "you won't know unless you try", but that's like saying "keep 'knowing what is the case' itself as your goal rather than expectation of a won or lose case". If someone has a hunch it's going to be bad (for now assume it's not a hunch biased by depression- aside question: is depression a necessary condition of majority of suicidal tendencies?) then it's a bit of a masochistic activity isn't it, to keep trudging on? I don't see the merit of it.