For an alternate (and more rigorous) view on the feedback between positive outlook and positive experience, see Martin Seligman's Learned Optimism. In it, he d

For an alternate (and more rigorous) view on the feedback between positive outlook and positive experience, see Martin Seligman's Learned Optimism. In it, he describes a number of experiments to show that how optimistic we are depends on how we choose to interpret past events. He also shows that increased optimism has measurable positive effects in many occupations and that a person's seemingly inherent level of optimism can usually be changed through a set of behavioral exercises. (However, he also points out that optimism can be a detriment in some circumstances.)