Santorum and Gingrich are the ones who are bought and paid for by K Street, their masters since 1995. Have they ever held a job outside of government, anyway? Lobbying gigs and writing books do not count, of course.
Of course Romney knows what it means to fear being fired. When you are an executive, you sometimes make mistakes because humans err. Those mistakes sometimes lead to firings. I am sure Romney made his fair share of mistakes and was probably close to being fired from time to time.
Furthermore, Romney held numerous summer jobs as a high school and college student. I am sure there were times when he made a mistake that he thought could potentially get him fired.