Fear.
Both the fear of the process of dying and the consequences of such an act in the afterlife.
The first one involves the possibility of not succeeding in my method and being condemned to continue in a much worse state (vegetative state and inability to have a choice and means to try again).
The second one is the belief that there is really no escape. I believe we are all infinite consciousness which incarnates into human bodies to go through the human experience. Our souls grow and evolve through multiple lives and experiencing emotions like love and, especially, suffering. "Playing God" this time around may force us to have to go through the same lessons and missions, possibly having to face even worse conditions in the next incarnation. I don't believe in or fear "Hell", but some form of punishment must be there awaiting. I used to be an atheist, and it would be much easier if I remained one. But 30+ years of research reshaped my belief system. And no spiritual entities (or Creator) look favorably to suicide. We may not be judged and be condemned to eternal damnation, like Christians believe, but we surely will have to pay one way or the other for failing our life mission and lessons. Unless suicide itself was one of those lessons, which is an extremely small probability.
