Happiness is subjective, nebulous. Optimism, on the other hand, can be objectively defined as the tendency to expect that life will be mostly good. Ideally, the two go hand in hand—but not necessarily. We can feel blue or blah yet recognize it as a passing cloud. We can be dissatisfied in our work or relationships but believe that better times lie ahead. We can acknowledge when a situation stinks—the canceled flight, the flat tire during rush hour—without concluding that the universe is permanently aligned against us.

Not surprisingly, people who look at life this way are less likely to be depressed or anxious, studies show
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Act Like an Optimist Improve Your Health - Page 1 - MSN Health & Fitness - Depression