My exam problems are seldom harder than problems seen in workshop and problem sets. In fact, many or your workshop problems are from old exams. They might seem harder because you have no help on your exams. If you feel strongly that the exams are much harder than the problem sets and workshop problems, it might indicate that you are relying on friends or solution manuals too much. You may not be confronting the practice problems on your own enough before seeking help. Also, keep in mind that some fraction of the problem set and workshop problems are designed to introduce you to something new. That subset of problems is somewhat easier than my exam problems, which seek to test your understanding. And, of course, once in a while I slip in an unintentionally nasty problem. Even though I edit and take my own exams, for security purposes I don't have others take them. So, once in a while something is harder than I intended. When this happens, I may stand by the problem knowing that you all got hit with it. In that case, it will not affect your standing in the class curve, in principle, because the whole class faced the same problem.