Don't confuse drive and passion. Drive pushes you forward. It's a duty, an obligation. Passion pulls you. It's the sense of connection you feel when the work you do expresses who you are. Only passion will get you through the tough times.
Randy Komisar, Kent L. Lineback (2001). “The Monk and the Riddle: The Art of Creating a Life While Making a Living”, p.93, Harvard Business Press