Is it disrupting your functioning or distressing you much then yes we need to do something about it.. I mean divide your time for studies, outdoor sports, meeting friends , listening music etc... If we keep on devoting too much time on one activity.. Unless you are pursuing it as your passion as career ..it keeps on repeating in your mind particularly when you are not doing anything.. Got it.. If it doesn't improve consult a Psychologist or Psychiatrist for the same.. Regards