I'd go so far to say that most people here on the forum want to be alive, too! No body wants to truly be dead, people just don't want to be in pain anymore, whether it's physical or psychological. I believe that people here on the forum have been left alone with their pain by doctors, friends, family and they don't see any other option to end the pain except by ending themselves.
The loss of belonging, the loss of love, of support, of understanding.. I think once that is gone for a prolonged period of time, and no one hears you scream for help anymore, no one takes your seriously anymore, that's when you know you're truly alone, and that's when people cannot enjoy life anymore. Humans are social creatures, we can persevere through horrific things, war, rape, loss of limbs, cancer, etc. But we are not made for isolation, being ostracised from 'our' people, from our support system, that is a death sentence.