Being under stress is like being stranded in a body of water. If you panic, it will cause you to flail around so that the water rushes into your lungs and creates further distress. Yet, by calmly collecting yourself and using controlled breathing you remain afloat with ease.
Usually people don't see beyond the surface of things and cannot understand more other than the obvious; they are used to judging a book by its cover, and that is why they don't hesitate to bully.
Vulnerability really means to be strong and secure enough within yourself that you are able to walk outside without your armor on. You are able to show up in life as just you. That is genuine strength and courage. Armor may look tough, but all it does is mask insecurity and fear.