Optimist means someone who puts a positive interpretation or spin on actions and events or one who looks for the best possible outcome: “He is successful because he is such an optimist and is always positive and hopeful about the future.”
Pessimist , on the other hand, means anyone who tends to emphasize the negative or to expect the worst possible outcome: “A pessimist always spreads negative energy around himself and thus, is liable to have least of friends.