California State University at Northridge refers to Scheier and Carver's 1985 definition of optimism. They describe an optimistic attitude as the tendency to expect good rather than bad outcomes from life situations, and a positive attitude toward problems approached.
While optimism and the expectation of good outcomes may improve a person's mood, a person can hold both optimistic and pessimistic views, and avoiding pessimistic thinking has a more important effect on mental health than encouraging optimistic thinking, says Ohio State University.
Optimism and happiness, often conflated, have different characteristics. While colloquially, the question of whether a glass is "half full" or "half empty" describes whether a person has an optimistic or pessimistic philosophy, Deirdre V. Lovecky, of the website Gifted Resource Center of New England, suggests that the question also involves the difference between convergent and divergent thinking.