Stress levels can go up and down quickly a person says the wrong thing at the wrong time. etc... We as instructors have to be very sensitive to the students everyday and how they are in the classroom. They may have had car trouble on the way in or the children are sick. We do not know what is going on. It is our responsibility to make sure that our students get out of the class what they need from the objectives and lesson plans. We are not baby sitters but we no need to have our hand on the pulse of the students. We try to ask questions and find out what the issue is and what resources we have that can help the student overcome this stress. It often just takes some talking to get things resolved.