From my first job, age issues. I was employed on the basis of my high school education results but lacked the experience {and maturity} to work well in a solicitor's office at 16.
From a restaurant when I was 18... too many narcotics, late nights and consequently late arrivals into work 😄
And from my last job at Norwich Union, except I was just laid off, rather than fired... I was only a temp anyway 😊