Can Optimism change Destiny?

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"Destiny refers to a predetermined course of events. It may be conceived as a predetermined future, whether in general or of an individual. It is a concept based on the belief that there is a fixed natural order to the universe." So destiny decides what we become. Is there a way to change our destiny? Is optimism the way? For those who do not know: "Optimism is "an inclination to put the most favorable construction upon actions and events or to anticipate the best possible outcome"." Does anticipating the best possible outcome, actually ensure the best possible outcome? In times of misery, we hear people consoling us with the old "look at the bright side" phrase. Seldom do we heed it, but is there more to it than meets the ear? Can "looking at the bright side", even if there is no bright side, create a bright side to look to? Can it pull us out of our misery? Can adopting the optimistic way of life change our life itself? Can it make us better people?