On Chanukah, the custom is to play with a dreidel. When one spins the dreidel, there is nothing that he can do to influence the dreidel to fall on the winning letter. Even if he is the best spinner in the world and spins the dreidel with all his might, he still cannot predict or arrange the outcome. Similarly, one works for a living, and one makes hishtadlus, but the results remain in Hashem's hands.