Give your mind a break for a few months. Try some shadowing and/or research in a field you think you might be interested in. Most importantly, relax and get ready to put all of your effort into MS2 from the beginning. It gets repeated over and over again on this site, but for some reason it just doesn't stick with a lot of people: the best way to do well on Step 1 is by doing well in your classes and getting a strong foundation going into dedicated. Studying over the summer will burn you out before Christmas of MS2.