The best thing one can have in a career is lack of fear of being fired.

True. This lack of fear comes from (1) being competent and productive, (2) being the expert in critical systems; the company would have a bad time if I was gone, (3) being hard to replace (it recently took us 6 months to find a second member of my team), (4) having good options available in the job market if I were to be fired.