Med school is a series of transitions.
First, you make the transition of becoming a med student. You get used to having more information dumped on you than you thought possible, finding that you can handle it but you're maxed out, and then getting more dumped on you and you handle that too! You'll probably study more that you ever thought possible, but will still have time to enjoy yourself, and will share your misery with your whole class.
Then, you get to the second year. You're not the peon anymore, you have first years asking you for advice and you get more information dumped on you, but it seems more relevant. You worry about and make it through step 1
Suddenly, you are in your first clinical rotation, which is a huge transition. You have to get used to getting to the hospital at an ungodly hour, seeing patients, writing notes and H&P and being called "doc". As you do your various rotations, you start over again with new residents, new expectations and new areas of focus. And as you approach your 4th year, you find your niche and decide what you want to do.
The you get to your 4th year. You do electives in your chosen field, maybe even some at other schools. You start to realize that, yeah, I do know some things and you find you are able to make some simple treatment decisions. And getting those first few interview invites are very exciting (in you email..."We believe you have the potential to be an excellent resident for our program"). 4th year is a blast...you acually have some responsibility for patient care, but you still don't really have any authority and rely on your residents to confirm that you are correct. Once your applications are in and you're doing the requried things that don't relate to your chosen specialty, the expectations of you are generally pretty low. And you start to think of yourself as a radiologist, pediatrician, surgeon, or whatever you will be going into. You'll learn from you classmates on your rotations...the radiology types will be able to teach you some stuff about reading x-rays, the medicine types will be up on treating diabetes and blood pressure, the neurology types will help you with your neuro exams.
Med school can be painful on a day to day basis, but overall the experience is pretty positive.