Pursue research that you truly believe has the potential to improve life. Knowing you are working toward something more than just a degree can help you find the drive to make it through the difficult or dry aspects of your time in graduate studies.
Your time in graduate studies will provide many opportunities, but don't lose touch with yourself. Take the time to do what you need to in order to maintain your sense of purpose and direction, then live out of that. Don't be afraid to try new things, but remember that no one can do everything. Be selective.
