When you got your paper back with a grade of F for plagiarism, you reacted in predictable fashion -- with indignant denial of any wrongdoing. You claimed “you cited everything” and denied that you had committed intentional plagiarism, or ever would.
This response is all too familiar to an experienced professor. Only once in my three decades of teaching has a student I caught plagiarizing owned up to it right away. And in that case, I believe (perhaps cynically) that she (a graduate student) thought a forthright confession might lead me to lighten the penalty. It didn’t; I failed her for the course and wrote her up. Indeed, I found out later that she had been caught plagiarizing by a colleague the previous term and let off lightly. I suspect that, because too many professors (many of them adjuncts fearful of student backlash) overlook or are unwilling to pursue plagiarism -- the process can be labor intensive, and it is always unpleasant -- cheating has become a way of life for many students, and they are genuinely surprised at being held responsible for it. So I don’t doubt that your shock is real.>>>