I had a teacher once. She wasn't the most brilliant teacher in the world, but good enough to have productive lessons with. I loved the subject and I liked the tutor. The best combination in academic world ever.
One day there was a lecture whose topic got my full attention. After returning home I started searching for more info trying to feed my curiosity. Not only had I gotten intellectually satisfied but also discovered something I thought the teacher may not be aware of. The next step was printing some stuff out and delivering it to my lecturer. Considering my colleagues' lack of enthusiasm, my 'display of interest' was a well planted seed. The teacher got really excited about having a keen listener and since then on she kept presenting me with various extras. All the lectures were directed straight to my ears and the eye contact got so constant I had an impression she didn't acknowledge the presence of about 40 other students in the room.
The worst part was about to come. Since the teacher ran out of interesting topics, my attention decreased proportionally. The tutors's enthusiasm didn't. Things kept coming into my hands. Printouts, copies, extra volumes of books. The collection of it was growing as fast as my interest was falling. My mentor expected too much from me. She saw in me someone interested in her knowledge, while my interest was limited to that single topic from which everything started. I got fed up. She saw my lack of interest and got hurt because she found out I wasn't the way she expected me to be. I got hurt finding out she got disappointed.
That was a great lesson. Expecting too much from others hurts. It clouds our judgment and gets the real person out of focus.