The Optimistic Bias (or Optimism Bias) is the human tendency to be positive and hopeful rather than realistic. People tend to be overly confident about the future; they overestimate the chance of positive events and underestimate the chance of negative events.
For example, someone may think they have a real chance at winning the lottery but very little chance of dying in a car accident, when actually the likelihood of dying in a car accident is much higher than winning a large lottery jackpot. This irrational tendency toward the positive brings both advantages and disadvantages. Overconfidence can boost self-esteem and ambition but can also lead to failed plans, financial difficulties, accidents, and other problems.