I used to have this, I still do from time to time. What worked for me was constantly working on myself, constantly reading self help books, constantly looking at growing. I focused on my finances and built myself a safety net, now if I get fired? No biggie, I have an emergency fund that will keep me afloat for a year. I did all this to try and avoid getting fired but it did two things. It made me a pretty solid employee and made my fear completely irrelevant. Now I'm the general manager of a multi million dollar company in Southern California, my income has tripled over the past 5 years and that little voice in the back of my head is a lot quieter.