How do you tell if school/classes plus part time jobs is too much? Right now I'm looking at taking 18 hours of classes in the fall and planning to work about 21 hours. How do you determine how many classes and hours at a job are too much and would interfere with getting good grades and mental health? I know each person has a different level, but how do you determine what your's is? I just don't want to reach that level by going into a crisis.