The Fantasy that "Passing is More Important than Learning" Somehow Translates Into Grades Not Being Important

Building on this earlier point it's not uncommon to see students complaining about how exams don't represent one's true knowledge, or that those who are successful have studied "for the test" but don't understand the material, or that grades don't really matter so long as one understands the material. The practical reality is that if you don't pass the course, you're not going to move on in academia, and in competitive circumstances (scholarships, graduate school competitions, etc.) the GPA is what is most often used to striate students. Learning is the "most" important thing, but examinations and grades are the tools that are used for objectively measuring that.



The Fantasy That a Miracle Reference Letter Will Make Up for Years of Mediocre Results

Reference letters do generally pull a lot of weight for graduate admissions, but I think there are a few points that often get missed by students. First, GPA correlates highly with how students are assessed in reference letters. It turns out most of those guys with the 4.00 GPA also have strong work ethic and outstanding research potential. Second, most reference letters aren't going to it can be very difficult to use reference letters to stratify candidates, particularly if you have a lot of candidates to sort through.



The Fantasy that You're Going to be the Next Einstein

You did well in high school. You're doing well as an undergraduate. You don't need to bother with labs, group work, or learning any of those pesky "applied" branches of physics because you're going to lock yourself in a room and single-handedly derive a theory of everything... from first principles... without ever having read any work that anyone else has done.

Unfortunately this common misconception is that physics is performed in some kind of intellectual vacuum and that lone individuals are going to come along and revolutionize the field with new ideas. While the notion is romantic, I think a lot of students fail to see that a lot of very smart people have been working on a lot of the big questions in physics for a very long time and we've reached a point where a lot of the new insights come through large collaborative efforts.



The Fantasy that the Courses You Chose This Semester Will Determine Your Career

While the educational path a student choses is likely to have an influence on a student's career, the fact that you're signing up for an astrophysics major as an undergraduate does not mean that all you have to do is pass your courses and you'll become an astrophysicist. Education and career tend to be two separate things. Careers result from the opportunities that are available when a person choses to search for one. Education will obviously influence those, but there's a lot of serendipity involved as well.