Some people are naturally gifted with photographic memories and will do amazing with minimal effort. Some people no matter how hard they work will never be in that top percentile. Most are somewhat in between where the harder and longer and smarter they work (including time management) the better they do. Many come to the conclusion that being in the top percentile just isn't worth the time commitment that it will take for them to get there.
There is no way you can know where you will fall in this spectrum until you're in it. All you can do is be prepared to work your tail off, be willing to adapt and change your strategy if necessary and accept that you might be one of those who can't hit the top no matter what.
For now the best thing you can do is get in the habit of working out regularly (most of the people I know have found that they do better when doing so, but its hard to make a new habit like this stick in medschool). I also read a bit about study techniques and time management ahead of medschool, as I had never *really* had to study before and found it helpful.
I have far from an "photographic" memory but I am an excellent student. I went for mastery of the material and not for quick memorization. Quick memorization puts information in your short term memory where it isn't likely to stay unless you use it daily. If you master the material and link it to your present knowledge base, it stays in there and you can recall it with a solid review.
I never let myself get behind the class. If I was sick or missed a study day, I went to where ever the class was and mastered that material. I could catch up on the weekend but I didn't use the weekdays to "play catch-up" because that was unproductive for my study strategies.
I studied in 50-minute bursts with 10-minutes of break in between. I never sat for hours staring at a page because after 50 minutes, my attention span was gone. I made sure that I tailored my study routine to my attention span. On those 10-minute breaks, I would run up and down a fight of stairs or get something to drink but I got completely away from my study materials to let my brain get a break.
I would also move around and pace as I recited things back to myself or to others. The pacing helped to relieve stress. I would master the material alone and then on study group days, we would discuss the material. Since our medical school had the most awesome syllabi in the world, we had everything that we needed to know in front of us when we studied. We didn't have to go searching through multiple books to find information.
I would preview before a lecture, take notes during the lecture and study the lecture later that day filling in anything that needed to be added for my understanding. I would then link the material to the preview for the next lecture. The next day, I would repeat the cycle. On weekends, I studied the previous weeks material as if the test were on that next Monday. By exam time, all I needed was a quick review and I was ready.
When I took exams, I would skim the entire test and answer the materials that I knew right off. If I couldn't answer a question in 30 seconds, I moved onto something else. I would then come back to unanswered questions after I had seen the entire exam. I was almost always the first or second person to finish an exam.
I also did not change answers unless there was something compelling that I noticed (clerical error). When one changes answers, they will invariably change 8 out of 10 answers from right to wrong and 2 out of 10 from wrong to right. In addition, I looked at questions carefully for answer clues which would lead me to the correct answer every time.
I have stone normal intelligence and memory but I maximized what I had. I also never let anyone (including myself) talk me into believing that I was somehow not going to be able to completely master the material. Your "inner voice" can sometimes "talk" you into believing that you are somehow inferior to other students which is far from the case. There is no material presented in any medical school that is unmasterable.
Finally, tune out the folks who boast about having "photographic" memories because they are the ones who "crash and burn" on Board exams. Run your own race and tend to your own work. Challenge yourself to hone what you do best and ignore the boasters who are trying to undermine your confidence. They are human just like you are and have to go from Point A to get to Point B.
You can decide (no matter what your past performance) that you are going to change your attitude and thinking as you approach your studies. Decide right now that you have every tool that you need to do well. Take a deep breath and start working on whatever the class is working on with the attitude that you will completely master it.