Natural Quitter Gene?

Ok so i think that all humans have a natural quitter gene that we haven't really studied much. I don't mean quitter as in procrastination. I don't know how to explain it well but here's an example. If you pick up a sharp knife (like a trench knife) and thought about stabbing yourself in the head with it and killing yourself, you would just put it down without really thinking about it and walk off. The quitter gene is that thing that makes you walk away from it for no apparent reason. Or if you were standing on the edge of a cliff and were going to jump to your death, you don't do it for some reason. Can somebody please explain what this quitter gene is and why we have it. And if you don't have anything good to say then don't say it