Jonah: You turned out to be a truly friendly person and a pleasure to have in class. That's why it was so unfortunate that you are so stupid. Students like you really depress me; I try to teach you, you try to learn, but it's just not happening. Oh well.
Horatio: Congratulations. You bombed every single assignment in the first half of the semester, but then turned yourself around and managed a B+ in the course. Usually, I'm cynical about the ability of students to change their habits. Looking through my grade sheets, the most obvious pattern is the lack of variation across time: students that do well almost always do well, and students that don't do well almost never do well. It's a subject on which I'm sure many bad students delude themselves, thinking they can improve on the next assignment even though they never do. But here you are, a perfect counterexample to my cynicism.
Nelson: I'm not your friend. When I see you on campus, I don't want you to use your outdoor voice and shout boisterous greetings to me. An understated smile is more than sufficient. Unnecessary and impromptu conversations with my students are about as satisfying as speaking to a goldfish. You ask me inane questions about teaching and the university, or even worse ask me questions about the course. You're not a bad person and I enjoy having you in my class, but to repeat myself, you're not my friend, so leave me alone.
Heloise: At the beginning of the semester, I had you pegged for the smart but rude student. Then I changed you to smart and rude but also lazy. Then I discovered you were stupid and rude. That was delightful to me, because then I had no guilt in giving you a C for the course. Take my hints, take my direct remarks to you, and shut up.