The definition of an optimist:
Someone, like me, who plans to get more done than time permits.
Having failed to achieve the impossible, someone, like me, who is sure everything will somehow get done anyway.
A more classical definition from the Mayo Clinic: "Optimism is the belief that good things will happen to you and that negative events are temporary setbacks to be overcome."
In one study, adults shown to be pessimists based on psychological tests had higher death rates over a 30-year period than those who were shown optimistic. No doubt, the optimists were healthier because they were more inclined to take good care of themselves.