First, look only at the the present, and just upcoming (i.e. no more than a few months away -- and only those items that require you to start acting sooner than later). Worrying about what will or will not happen in your junior year does what for your motivation? For your energy levels? Etc.
Second, as shared above, time management.
Your syllabus should be driving your schedule. You need to determine how much study time is needed for each class (a "general" rule of thumb is a minimum of two hours of study time per week for each hour of lecture or lab time; you may find some classes require less, and some classes require far far more). You then set up a calendar system breaking down when you have classes, when you will need to start working on what specific papers, when you will study, when you might study more because of a test, etc.
Then you follow your calendar as best as possible only deviating for true emergencies or if you really are that far ahead you can give yourself a short break.
Do try to map out physical activities such as walking, running, working out, etc. -- not just for staying in shape, but giving your mind recovery time.