Believe it or not, every med student at the beginning of M3 year will feel uneasy like you about starting on the wards. Regardless of the knowledge you have in your brain, the wards represent a novel environment for each student. Students , in order to do well, must be able to quickly adapt to this new working environment. Doing well 3rd year doesn't depend on actual knowledge as much as you would think. Enthusiasm, work ethic, and being easy to work with are just as important.
Nonetheless, as an MSTP student just returning to the wards, there will be a huge sense of insecurity. In essence, you have forgotten 90+% of the things you learned many years ago in the first two years of med school. I felt the exact same way. By the time I returned to the wards, drugs had changed. Some of the clinical trials that were going on when I was an M1 and M2 had been completed and I had to learn these new things as well.
My advice to you is to focus on each rotation one at a time. Don't get to caught up on trying to catch up completely to your peers. For example, I started on neurology. So before I hit the wards, I reviewed cranial nerve function and very very basic pathways (pain/temp sensation, proprioception, and motor). I also reviewed in detail the full neurological exam (which I never really used in its entirety). In this regard, I wanted to start on an "easy" rotation like neuro, psych, and family practice. It was a good way to ease back into the clinical mindset. And during these warmup rotations, I still read about the diseases I encountered in the day (well, not really but that's what you're supposed to do).
Now, if your first rotation is surgery or internal medicine, that is a whole daunting task to warm up for. However, the same work ethic applies. If you get a patient, read about the patient, differential diagnosis, and management. 2nd year of med school does NOT teach you management. Step 1 boards do NOT teach you management. Everybody is on the same ground when it comes down to knowledge regarding management of disease so you just have to trudge through it like everyone else. It sucks but 3rd year is just one year.
I'll add to this post if I can come up with any other pieces of advice.
Oh, I would be familiar as to how to prepare an H&P and oral presentations. You can be really smart and know your stuff but if your presentations and writeups look disorganized, then you're in a world of hurt come evaluation time. I suggest Introduction to the Wards by Paul Fine as a nice and easy book to read. It tells you the tricks about being a good med student. There's also a book by Samir Desai (which I didn't read but I heard was good) about the 100 most common mistakes M3's make. I think books like these will be of far more use to you given where you stand right now. Reviewing the cardinal symptoms of pheochromocytoma or MENIIb will be of little use at this stage of the game.
