What do you wish someone had told you before applying to medical school?

This is not the end-all be-all. Getting into medical school seems like the only thing that matters in the moment, but in reality you are a much more than just an applicant / premed. It will work itself out eventually. Sure, it might take one or two attempts to get accepted, but it will work out. Try to still enjoy life and develop yourself as a human. Find hobbies, be social, stay healthy and physically active. These are all skills that you will need to continue working on whether you're in medicine or not, and being a multifaceted human will make your life much more enjoyable (and a much more attractive candidate for schools as well).

I didn't have many mentors when applying to med school, so everything I learned was from online forums and from advisors. Because of that, most of the advice I got was on preparing the application. But something I've learned is that when you're spending so much time optimizing and perfecting every part of your app, it can be easy to forget that med schools want to select for people, not checklists. I think the advice I see on this is to find activities that ultimately form a narrative, but honestly, I believe not everything you spend your time doing has to be geared towards medicine. Joining a non-medical club, taking interesting and unrelated courses, or even spending time on hobbies are what separate the cookie cutter applicants from real human being and make adcoms appreciate you as a person and not as a completed checklist.