I was in a very similar boat to you going into year 1. Had gotten off a waitlist, was super nervous about not doing well, and wanted any advice I could get about "how not to fail." Truth is there isn't a single solid answer. Everyone is different. Some people are great students and they collapse in the first year. Some people were terrible/mediocre in college and they become the top percentile.
The only really good advice I can give you is enter your first semester with no expectations. Don't assume you're gonna be the best, and for goodness sake do NOT assume you will be the worst or are predestined to fail--your frame of mind is more important than you know so on that note stop asking how you can "avoid failing" and frame it in your head as "how can I best succeed." That may sound like some lame woo-woo motivational pep talk, but you can't do medical school expecting to fail at every turn.
You're also going to get a lot of advice, solicited and unsolicited, online and from your classmates. Take it all with a grain of salt. Some people tell you they are getting straight As without trying--but actually they're failing. Some people will tell you how they're acing classes and doing 1000 anki cards a day and are already on their 2nd pass of board materials by Christmas of first year. Some of those people actually are doing that because they're amazing.
As a whole, I tried to ignore all that. The most important thing about the first semester and first year is finding out what WORKS for you. I had some success in some areas, less success in others (aka did well in some classes, did terrible in some others). Eventually I started to discover what worked for me to get decent grades and to best curb my anxiety. I think you will too. But good lord, do not stress yourself out by saying you're the only who is struggling. If something does not work for you, be willing to change how you study/handle things, but remember that you are not alone. No one else in your class has gone through medical school either.
Rant aside:
-Don't expect perfection, but don't expect failure
-Do everything to prepare yourself for uncertainty in the first 1-2 semesters
-Find some good ways to handle stress (friends, exercise)
-Get plenty of sleep on a regular basis (though pulling a late night cram session is okay)
-If you're struggling, reach out for help and be able to change things up