Who is the "Self" in Self Sabotage?

You heard about a new position in your company, an exciting position that could lead to the unique career opportunity you always dreamed of.
At first, you got excited as you envisioned yourself stepping into that role, confidant and self-assured. You felt that rush of adrenaline that comes with positive new challenges.
Then a voice popped up in your head. It said,” You can’t do this. You are not qualified. They will look at your resume and point out all the flaws in your experience and education. You will look foolish. You are not good enough. Some people are more qualified. You don’t stand a chance”.