You need to constantly prove yourself everyday. Lets put it this way. If I don't show up for work and I did well on the interview. I'm not proving myself aren't

You need to constantly prove yourself everyday. Lets put it this way. If I don't show up for work and I did well on the interview. I'm not proving myself aren't I? If I do horrible work, if my code is buggy and full of errors then what am I? No manager will fight for that despite a strong interview. This is simple logic and common sense. Obviously the person in the original posting proved himself.