No worries!
I think the most challenging is just keeping up with the sheer amount of information that you need to know in a very short amount of time. The saying about drinking out of the firehose is definitely true.
Unfortunately achieving the scores you want is really different for everyone, the first few months are basically just you trying to figure out how to study as your pre-medschool methods are likely not going to work anymore. Everyone goes through that and it is totally normal. Just try out different methods and you'll find what works for you. This also kind of changes per block, so it is an ongoing challenge.
Definitely do not prep anything now, just enjoy your time off and do all the things you need/want to do. Maybe get your vaccines up to date but that's all.