...Just work hard and learn as much as you can. Best of luck with your endeavours.
This is really the bottom line.
For the OP,
The programs are hard, and they are that way because you will someday be responsible for people's health. Your goal should just be to assimilate as much knowledge as you can. Everyone has different natural talent levels and different strong suits (rote memorization, conceptual thinking, visual learning, short/long term memory, etc). You can study to ace the tests, and you can also study to understand the material. The two often go hand in hand, but not always.
Some courses like anat, pharm, or micro are pretty much just straight memorization. You will spend a ton of time memorizing medical terms, buzzwords, and numbers. Nobody will remember it all, so you just do the best you can. Other areas of study like physio or biomechanics are more conceptual where there is not a ton to memorize, yet you have to understand and think through a logical process.
Every course is there for a reason, but some are obviously more essential and more represented on the boards. In semesters where you get really crunched, make sure you are getting the most of your key classes: anatomy, path, and pharm. If you bring strong applicable knowledge of those subjects into clinic courses and clinic itself, you will probably do very well.