I had a student in a literature class who--even though she ended up with a good grade in the class--I felt did not "get it" in some important way.

This student is taking an on-line class that I teach this semester--a course designed by another person. (I basically just grade.) My former student, who I did not have high expectations for, just aced a big assignment. A big part of her success was due to her knowledge of poetic forms and techniques--something she learned in my class.

I rarely teach the same students twice, and it's wonderful at this moment to see that my student learned and improved in my class. And she retained something!

Even if you won't see the benefit of your efforts next semester directly, likely another professor will. It's a happy thought.