As with most schools, unfortunately, some students have found it necessary to treat classes and grades like its a competition - we refer to these people as "gunners". There are very few of them here though, and you'll be surprised how a majority of your class is normal and more like you than you would expect. Then again, we are all medical students, we all have at least a little "type-A" in us.
It is VERY possible to study enough to do very well and still have time to do all the things you enjoy - even grabbing a few drinks on the weekend. The key for your first two years isn't to get the best grade - study for your own knowledge and the for the benefit of your career. Also try to avoid the "gunners" because all they talk about 24/7 is class related things - it will frustrate you and stress you out being around these machines.
The course directors will set the percentile at the beginning of the course for H/HP/P/F - its usually Top 10% Honors, Next 15% High Pass and the rest Pass and Fail. Don't worry too much about grades though - I can't stress that enough. You've made it to medical school - now just learn the science and medicine for you and your patients.