It's really relatable! We are all the products of 3.5 billion years of evolution and of course, our brains will try and keep us alive at any cost.
The way I see it is this: I will not do it until I am 100% sure the time is right for me to do so. I am not a half-hearted attempts kind of person, I will not do anything but then in the end get the lethal stuff and really try to kill myself. Many people for example, take benzos or some other not so lethal substance in attempts half-knowing that they will not die in order to get help, or to make family members aware of their suffering etc. It is not the case often, but it does happen every once in a while. That's not the path for me. If I have any doubts about it, then I will live on some more. It's not a race, maybe things will change. So only do it if you have the feeling nothing is ever going to change and you cannot go on for one second longer. Then the time has come. If you are still debating it, don't do it. It is not right for you. Who knows-I have never really tried to do so and maybe my opinion will change if I try.