This is a joke I sometimes make about the general biology class I teach. An astounding number of students enter their freshman year intent on making it to the doctor status. Several don't even make it through general biology, and a number say "well, I like biology, but I don't know if I'm cut out for medicine anymore." I like to think my class just shows them what they need to learn about themselves.
I read PhD comics, and the recent two days of strips have hit home. Celia, an engineering grad student, has been teaching a difficult class this semester full of students who don't attend review sessions but still whine about grades.