1. If you aren't getting at least 6-7 hours of sleep every night you're doing it wrong, I promise. You will be more efficient over the long haul if you take care of yourself. Unless you're on a mandatory 36 hour shift or something (hopefully your med school doesn't have those). Likewise, studying on an exercise bike for 30 minutes every other day, or lifting in the gym 30 minutes three times a week will be AMAZING for your mood and productivity.
following, in no particular order:
-Figure out what works for you and keep doing that. Lots of people above you will probably give you terrible advice. They're well-meaning, but ignore them.
-Your curriculum will probably not prepare you to pass board exams. Ignore pathoma, sketchy, UWorld, etc at your own peril.
-If you want to match a competitive specialty, what matters is your step 2 score and research. Everything else (including class grades) is secondary. I don't think focusing on boards and useless research will make you a better doctor, but it's how the game is played, and your med school administration probably does not know this (at least mine doesn't)
-If you don't want to match something competitive: study until you are safely passing (As and Bs, or maybe Bs and Cs), and make sure you're prepping for boards (UFAPS/etc), and then go enjoy your life. Don't get divorced because you want to make As instead of Bs, especially if you're going for FM/IM/peds/EM/gen surg.