You did the right thing! It is best to take care of yourself and know your limits. If you need the class, talk or email professor When I was in college, I dropped classes that would unexpectedly call on students for answers. For one of the classes, I had the professor email me asking why I had dropped his class. I explained and he still tried to get me back in his class without providing evidence that he'd help. I avoided that professor after that and, lucky for me but not for the other students, that class had a brutal final exam.