Let say you are very rich, very handsome, very smart, very healty, with the best job, etc. All most what a normal person will desire. But you are a pesimistic. Very pesimistic. - All your life you will never be happy. Allways you will find something bad in good (or normal, usual) things. Every day your life will be a nightmare.
At the opposite, optimists people will be happy in every day, even if they are sick, or poor, or not beautiful, etc. They will allways will find a way to enjoy of life.
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