excluding spies and other carriers of information "not for everyone," idiots of the "I'm not afraid" / "I'm not afraid to die for my god" type, and blackmailers of the "you'll regret it when I'm gone" variety, I agree with this:

the general stimulus for suicide is unbearable mental pain

In this case, the answer is obvious – to get rid of the pain, strength is not needed. On the other hand, "unbearable mental pain" often turns out to be not such an insurmountable problem; it can be solved. It could have been solved. By applying some effort.

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You won't know if there's a better world until you die.

But what's the point of killing yourself for that? Sooner or later, you'll die anyway.