Why quit now? Go till your body makes you stop. Seriously: RSD is unpredictable. If you are not strong enough to handle classes this summer, then you will know it from your own experience, not from a doctor or anybody else telling you. You will not regret trying. You might regret not trying. Also, if your RSD progresses, you may regret that you did not seize this time to trying doing something you really want to do. Carpe diem!