A great leader feels very passionately about his work, and it is that passion that drives him to excel. The mentor must convey this passion to the student. Nothing gets done with the passive approach. Passion increases willpower. The mentor must have enthusiasm if he expects the student to.
Enthusiasm breeds enthusiasm.
When the student is around someone that has passion and enthusiasm, he is going to catch it. If he has been touched by it, he will immediately recognize when it is not present. The world is full of talented individuals who have not excelled because they don't have the proper discipline. Likewise, the world is full of less talented individuals who have far surpassed their more talented peers, simply because they were disciplined. We could call this care, but I prefer to call it love.