An optimistic person expects all the best things to happen! Is it raining money yet? A pessimistic person is a downer. Who cares if it's raining money? They'll never get any.
Optimistic people see the best in the world. Optimistic ideas have been around for a while — Voltaire's "Candide" (1759) mocked them thoroughly. Here's an optimistic quote from Ralph Waldo Emerson: "Write it on your heart that every day is the best day in the year." Here are some more recent examples from the news:
"It's been so positive…He's always optimistic, always hungry for the next one." (Washington Times)
"It's an optimistic assessment that clashes hard with the reality on the ground." (Los Angeles Times)
Abandon all hope ye who enter here! A pessimistic person expects the worst in every situation. Doom and gloom rule a pessimistic attitude. In business, a pessimistic mood prevents people from investing. If you're pessimistic, you see a beautiful waterfall and assume you're going to die in it. Here are some examples of the word:
"Designed to cope with the most pessimistic nightmare of an apocalypse, a day spent here is not destined to be uplifting." ( BBC)
"There has also been a smaller—yet still statistically significant—rise in the frequency of negative words, such as 'disappointing' and 'pessimistic'." (Nature)
These words often show up together:
"And my personal philosophy is I'd rather be optimistic and wrong rather than pessimistic and right." (Time)
"A higher life expectancy estimate is optimistic for the human condition, but pessimistic for the Social Security Trust Fund." (New York Times)
Most people are a little of both, and you can certainly be optimistic — you just learned new words! Or pessimistic — you'll probably just forget them, though. Sigh.