If you like what you're doing you will do well! Try to remember that even your professors were once students and got very far.
Try to read many books but also ask many questions on your clinical rotations. Find a group of friends and help each other out with your studies.
If you find it hard to get motivated, try to see yourself as an accomplished doctor, watch medical shows...
Find things to do outside medicine (hobbies, sports etc) because this will give you a better perspective on dealing with your patients and with your own stress.
Good luck with your studies!