I think knowing if students are either happen or sad in a class is a very important thing because that lets you know as a teacher if you are doing a good job at teaching or not. As teachers your suppose to make your students feel happen and excited to be able to learn. If you (the teacher) comes to class sad or in any negative way the class will feel the same and will not want to work because of how they are feeling. Then there can always be that one student in the back of the class all alone because he doesn't know nobody or because something is wong with him you should make him feel happy or even ask him what's wrong because no matter what you do not know what is wrong with a person unless you talk to that person and actually listen to what they are saying. You also have to understand wha they are feeling to be able to know how to handle that situation because if you don't and don't know what to do, you will make the other person feel even more bad about their self.