This book teaches something important:
Vulnerability is the greatest Courage ~ Dan Millman
At first glance this may sound absurd, because most often vulnerability is equated with weakness. However, when you think about it, it's not an art to 'raise your guard' or 'put on a mask'. Suddenly it appears that remaining open to everything around us is more difficult than it might seem, and indeed it is a trait of those most courageous.
I would also add that an importance of sensitivity is mentioned many times throughout Dan Millman's books, including a sentence from the beginning of this note.