Sometimes, while talking to a friend, I will hear him or her express doubt in his or her abilities and success. I will tilt my head, wondering if my friend is putting me on; how could such a smart, successful person say such a thing? On other occasions, the roles will be reversed: I express doubt in myself, and my friend cannot see how I would feel so.
Just recently I have learned that this phenomenon has a name: Impostor Syndrome. People who are capable and successful often worry that they are an impostor of their own achievements. They attribute their success to luck, downplay the significance of their success, and worry that their perceived incompetence will be found out. The Caltech Counseling Center has an excellent description of the syndrome, as does Dr. Pauline Rose Clance, who, along with Dr. Suzanne Imes, first suggested the concept.
There is another side to this: feeling like an impostor actually shows how strong you are. Self-doubt makes all tasks harder, and forging ahead despite it requires resilience and passion. To even feel like an impostor in the first place, you must find yourself in a position you believe is worthy of recognition, which requires dedication to gain and hold. Consider how you want to focus your courage, and redirect it towards what drives your passion.