The fact that numbers are so important. Doubly stressful if you are applying MD/PhD where even non-"top tier" programs have 3.8/516 median scores and like 50% of the class taking 2 gap years to build research experience. It was a constant source of stress throughout college that took a lot of mental effort and energy to suppress. I never wanted to make decisions about what I studied or what professor I took because I was a pre-med. As a result, I ended up taking a lot of elective courses, challenging professors, and difficult classes that were not required for my major. I ended up OK stats-wise, but it really bothers me that you essentially have to make a choice between A) challenging yourself and moving out of your intellectual comfort zone (you know, what you're *supposed* to do during college?) but being a walking stressball at the end of every semester and B) min/maxing your med school application.
There were some points freshman year where the stress of maintaining a perfect GPA was so great, it literally prevented me from studying, sleeping, or enjoying myself whatsoever. Luckily, I had a fantastic English professor who took it upon himself to beat perfectionism out of his students and instill a little bit of perspective about what it means to be a good college student.
To be completely honest, thinking about the process from an abstract, structural perspective is very depressing. I look forward to applying to get it over with. I have no positive feelings about enjoying the process. I don't feel hopeful about the future of medicine or science, but I love being in the clinic, working with patients, and doing science. I don't feel like schools care about seriously reforming the process or improving it, and that they are happy with the way things are. I generally don't like pre-meds I've met IRL so I'm also not particularly confident I'll even like my classmates in medical school. Again, these are just feelings, I don't think they are necessarily valid.