What distinguishes Olympic athletes from enthusiastic athletes is that they don't have passion; they have dedication. Day in, day out, regardless of how they feel, they follow a structured training plan. Feeling enthusiastic on a day scheduled for resting? Tough, you rest. Feeling down on a day scheduled for training? Tough, you train. It's not about being passionate, it's about what our fathers tended to call stick-to-it-ivness.

Perhaps a better example is going for a doctorate. Everyone with a PhD will tell you the critical requirement for getting a PhD (if they're being honest) is neither raw intelligence (beyond what you needed for the primary degree), nor passion for the topic, but the dedication to spend four to six years of your life in the focussed, deliberate and pragmatic pursuit of a goal. Passion will do nothing but cripple your efforts - you have to remain objective, be able to drop an approach if it's not proving useful without a second thought, and not get married to the central thesis lest it distort your results.

Same principle applies to programming. Dedication, professionalism, these are the real virtues - passion just produces fanboys for whatever the method de jour is.