Should I quit this job I just started?

I just started a Summer job at Dairy Queen two days ago (I am a college student who is back home for the Summer). I don't need the money but wanted some extra cash and something to do, so I applied and was hired full-time on the spot. The restaurant is severely understaffed, so I know I'm needed, but I want to leave. The manager is bi-polar (yelling at us for literally no reason except ones she made up), the business is overly slow, an employee sliced his hand open and was told to suck it up and wear extra gloves, and I would really like to take Summer courses so I can graduate early. Also, I am upset whenever I come home, so my relationships with family and friends are strained. Does anyone have any suggestions as to what I should do? Also, if I was going to quit, what would be the best way to go abut it?