When your experience tells you that something is going to hurt you, your brain will figure out how to avoid and survive it. It will naturally kick in. Again, you can learn to work around that, or maybe even ignore it, but expecting your brain to magically stop reacting is asking yourself to not be human.
Maybe instead of expecting that from yourself, or anyone, give your brain some credit for going into survival mode, for keeping you alive, and be gentle with yourself.
Even if you are in a situation where acting out of fear is silly, it’s OK to feel the fear.