I appreciate your curiosity, but the problem here is precisely that you don't know how it works. You make declarative statements about what is or isn't possible, despite the fact that you're asking how the process works. It's like trying to understand future propulsion engines by looking at a V2 rocket. You're assuming how something works and then getting confused when it doesn't add up. I'm not claiming to be an expert on the specific subject of shifting, but I will say this. Firstly, it is not just a fight-or-flight response. It could be triggered that way, but there's no reason why it would be restricted to a body's panic mode. It's something you willfully do and, like anything (both physical and non-physical), it requires exercise. I like to use the analogy of running. If you do it often, then you can just go right into it. If you do it less often and go into it, you'll feel it later. If you never do it, then it will be difficult to even attempt. Of course, it's more complicated than running. It's the manipulation of one's full biomass as well as nearby energy (as mass is just another form of energy). It sounds difficult and strange, but that's because it's not natural to you. I imagine explaining how a bird flies to someone who has never seen a bird would have the same effect. If you walk away with one thing, just keep in mind that you can't judge what you don't know based on the standards of what you know. It's okay to not know things. Literally everyone has to live with it, even if most are in denial.