Game theory presupposes that there are at least two players with conflicting interests and the outcome of the game depends on the decisions of all the players, while the decision theory presumes that the decision of only one agent aff ects the outcome because the decision maker (group or individual) has to reckon with only a passive environment (i.e. he has no opponent). In this study we treat life as a game with the human being on one side and the Nature (not the passive environment) on the other. Using the results of the game theory, it is shown that an optimum strategy for life is: "Do thy duty, reward is not thy concern" i.e. to engage in the performance of one's duty without caring for success or failure.