i graduated med school in 1993 and have been a family physician for 20 years.
i hear that you're anxious about the medical curriculum and you're absolutely correct that it can be stressful.
here are some possible avenues.
1) education. the more biology and chemistry courses the better. learn how to use a microscope well. look into taking some online courses. edX.org is a good site. when you're in college the health professions counselor can provide you with a list of all of the medical school prerequisite courses. there will also be some "recommended" courses. take as many of those recommended courses as you can.
2) communication skills. learn a foreign language or sign language. also, try to find a course on "medical terminology." that was by far the most useful pre-med course i ever took.
3) history. read biographies on famous doctors. or books by doctors about their experiences with medical education or their careers. google can give you some titles. or visit your local library.
4) customer service work. a job interacting with customers will prepare you to interact with patients.
5) medical experience. write letters to hometown physicians requesting to interview them after work. ask their experiences and advice about college, med school, residency, the medical field in general. if things go well ask them if you can shadow them for a day. if possible do this with docs in several different specialties. try to speak with a med student and a medical resident if you can.
6) specialty knowledge. skim online articles about current happenings in medicine. especially ones about specialties that interested you.
7) optional: health care policy. nowadays in the US it's not a bad idea to know something about medicare, medicaid, insurance, and how those things came to be what they are. by extension you'll learn something about medical ethics.