If someone told you that biochemistry was the hardest course in medical school and that you were guaranteed to fail, what would you do? You still have to take it. Spending time worrying about the difficulty of upcoming courses is a waste of time. You do what you have to do and give it your best shot. Whether something is easy or difficult is largely related to the learning style/characteristics of the individual in question.
For example, most students find Physical Diagnosis to be fairly straightforward and interesting. One of the MD/Ph.D folks at our school failed that course (no one else even came close to failing). He easily moved through the other first and second year courses but failed Physical Diagnosis (had to re-mediate twice).
Concentrate on the block that you are doing and stop worrying about what is ahead. When you get to the next block, face it with an open mind and the confidence that you can figure out what to do to pass and master the material. People who decide that something is "hard" or that they "can't" get throught something usually find that the subject matter is more difficult or they fulfill their prophecy. Don't be one of these folks.