"Please don not let this course to be the worst and black point in my life."
This e-mail disturbs me. First, it is borderline suicidal (which is not, in itself, a big deal because students here are masters of drama... If I said, "I'll give you an A if you can cry and produce real tears" I'm pretty sure most would walk out with an A.) Second, this was a student who actually tried. She never missed a class and never came late. She sat in the front row and took notes.
A teacher wants to believe that diligent students will understand the material. To have proof otherwise is disturbing.