don't worry about it; it's just school like you've been doing for all these years.
you go to class in the morning, sit down and try to pay attention to a lecturer mumbling and bumbling through slide after slide of powerpoint. People around you crack jokes, other people stare at them for being distracting. During breaks between classes everyone goes outside and chills for ten minutes, then back to the grind. I think we had anatomy lab too the first day, pretty cool.
The main difference is the volume; some exams are similar to undergrad but they're over WAY more material and the questions require a deeper understanding. There are very few "gimme" questions on med school exams. It's like all the other school you've done but an order of magnitude more involved. Impossible to describe but you'll find out soon enough. I actually think it's really chill most of the time; after exams I take at least week off and just relax, so it's like having spring break every 5 weeks. :-D.