No one can know for sure but I'd say the following won't put them in a strong position:
- No hope left. I'd say that's the major one. Really, you can probably get over other things so long as there is some hope left.
- Treatment resistant illness- physical or mental, or both.
- An unwillingness to try to make things better. I think it takes effort- lots of it to change life around. I think very few good things just appear magically for us. So, there's that whole: 'The definition of insanity is doing the same thing over and over and expecting different results.' Attributed to Einstein but could be Mark Twain or Ben Franklin.
- A nihilistic philosophy I'd say will always make them at odds with this world and- they'll either not do anything constructive because- what's the point? Or, they'll resent having to do things like work and study because- what's the point?
- Little or no enjoyment left in anything this world has to offer. Leaving only suffering.
The first point is so important, though I agree with all of these 100%. If a person is not satisfied with life, the hope that tomorrow brings about a better day can keep them trudging along. Once you've lost your dreams and your hopes for the future, then what motivation is left?
I think an impulsive person can be talked down and persuaded to keep living if they have hope that things can change. When someone ends up in a situation where they cannot find even a glimmer of hope, that is when things become truly dire, I feel. When I first joined this site, I would cling to various hopes, like a new test or treatment, but these would inevitably never pan out and leave me feeling worse each time this hope was crushed.
Constantly wishing for things to get better then being let down over and over again when the improvement you've worked towards doesn't manifest is a huge killer of the spirit. I think once things get that bad it is hard to come back from, unless something appears that can rekindle those hopes.