Optimism boosts your energy and focuses your sights on reaching your goals, rather than wallowing in your setbacks.
Denis WaitleyPositive self-expectancy is the first, most outwardly identifiable quality of a top-achieving, winning human being. Positive self-expectancy is pure and simple optimism: real enthusiasm for everything you do... [while] expecting the most favorable result from your own actions. There never was a winner who didn't expect to win in advance. Winners understand that life is a self-fulfilling prophecy. And they know that you usually get what you expect in the long run.
Denis Waitley