I know.....CNA work is hard on the body and mind. 12 hour shifts and overtime added to that in addition with your school work is a bubble ready to burst. But you have to stick to your guns and say no. You are a STUDENT....use that only. If they can't understand that then you may very well be better off looking elsewhere for employment. Because you may need a day off before a major test or if you do get too stressed....they need to take care of their employees. Good luck to you.... but try not to push your limits, you do not want to have an episode. It sounds like you know your triggers and that is half the battle right?