Hey Reader! I'm a big believer in the power of positive thinking. Being optimistic won't solve your problems, but it will make it easier to weather them. And — as it turns out — happiness is contagious. Are you happy more often than not? The science of happiness asserts that if you've got optimistic parents, then you're likely predisposed to also look on the sunny side. But even if your parents were negative nellies, 50% of the reason why you're happy or not lies under your control. Studies...