Practically everyone knows that med school is difficult and that the exams are fairly intense. People even joke about how med students become intimately attached to caffeine during exam season just to survive (funny because it's true I guess...).
One of the first things you should realize as a med student is that these exams are different from any exams you have taken before in undergrad. I did my undergraduate degree in engineering, another degree that is universally considered to be difficult, but even though I had up to 9 courses in a term, those exams were much easier. The difficulty in medical school exams comes from the amount of content, not necessarily the difficulty of the material. The key difference from undergrad is that you can review an entire undergrad class in 3 days if you have kept up throughout the year and you can buckle down and focus during crunch time. After those 3 days, you can known EVERYTHING that you are expected to know for that course.
In med school, you can spend three weeks, theoretically, studying for a single course and still not memorize everything you need to know (I say theoretically because you also have several other courses you need to study for at the same time so you can't actually devote three weeks to a single course). The best thing you can do for yourself as a med student is to accept that you won't know every detail of every subject that you can be tested on. Coming to terms with this fact will help you study effectively without stressing out. Many of our exams are multiple choice, so if you focus on understanding basic principles you can often do a good job of narrowing down the correct answers.