Fake it till you make it?

I am an introvert and also have extremely high standards for myself and am very hard on myself. I have a pretty extroverted job (teacher) and now I am in a position where I have to be more of a leader/authority. I am struggling with anxiety and self-doubt. I know I can grow from being in this sort of position, but it is so hard being out of my comfort zone and feeling like I'm not good enough. Just curious if anyone has had similar feelings about your careers or experience overcoming these types of self-doubts?