As a game master, I think it is a valuable exercise to take some time to think about your assumptions.
Consider a concept or principle that you believe to be an unassailable truth when it comes to game mastering. Write it down. Now assault it. Interrogate yourself on the veracity of this principle.
Don’t be lazy about it. Really go at it.
What you may find is the position you previously held is not quite so certain. Not so clear. There may be subtle distinctions, exceptions or (best of all) you might have been completely wrong.