Join the crowd. You're not alone in feeling anxious and insecure about being moved into a bigger job. Plenty of competent managers harbor fears that their "inadequacy" will be found out, causing their careers to crash. The first thing to remember is that, as boss, you are dealing from a position of strength. So whatever you do, don't appear defensive, apologetic, paranoid, anxious, or panicked. To whatever degree you have those feelings, save them for your career coach or therapist.