Vulnerability means to show yourself to others completely and utterly without holding back for fear of rejection or judgment. It means to say “here I am, flesh and bones. In other words it's like when you're nice to a friend and you show that friend your kindness but they take advantage of you and you continue being their friend without reading between the lines and realizing that so-called friend isn't a real friend. You want to fit in so you hold back because of fear or judgment. That's vulnerability.