Self-confidence. The most fragile thing on earth. I have seen the most self-confident, capable people develop cracks in their self-image, doubting their ability to handle the simplest of tasks. Sadly, our image of ourselves and our abilities is tied to the way others perceive us. So if you get passed over for a well-deserved promotion time and again, or see others who are clearly far less capable than you outshine you, its only natural that in time you will begin to question