About the only way I know to improve one's chances of avoiding a surge of fear in an emergency is to imagine oneself in such a situation, in as much detail as possible. You may not be able to duplicate all the conditions of a real emergency in advance, for example you wouldn't set a grease fire in your kitchen to learn how to put one out. But mental practice in dealing with a dangerous event does help to make it seem more familiar and manageable, even if you've never actually experienced it before.