It's wrong to say things to make someone feel inferior.
Clyde is a teacher who is working with a student that has trouble with a particular subject.
Clyde wants the student to not worry about his performance.
Clyde tells the student that he will understand it with time and practice.
"Clyde tells the student that not everyone can do it and not to feel bad if he doesn't have the ""knack"" for it."
The student continues pushing until he masters the content, feeling good about himself.
The student thinks that he will never be able to do it and gives up.