A lot of times your college professor is the last person you should listen to. This is especially true when it comes to education professors.
A lot of college professors never had much teaching experience themselves. The ones who did may have been in the classroom decades ago. As a result, they are out of touch with the reality of today's classroom environment.
I am not saying that you shouldn't listen to anything your professors tell you. A lot of it is valuable information. Just don't assume that everything they say is right.
Take what your college professors tell you with a grain of salt. And if they tell you something like "don't smile until Christmas," demand that they retire immediately.
Future teachers will be glad you did.