We believe things will go better for us than for everyone else, even without evidence to back it up.
Most people believe they're less likely than others to have an accident, lose their job, or get divorced, and more likely than average to have a successful career. Statistically, not everyone can be right. Optimism bias is the tendency to overestimate the likelihood that positive events will happen to us, and underestimate the likelihood of negative ones, compared to other people.
In a classic study, college students were asked to compare their own likelihood of experiencing various future events, good and bad, with that of their classmates. On average, they rated themselves as significantly more likely to experience positive events (having a good first home, a satisfying job after graduating) and less likely to experience negative events (divorce, illness, car accidents), with no objective basis for that difference.
Holding an optimistic view of one's own future reduces anxiety and sustains the motivation to act, even though it comes at the cost of underestimating real risks, like those of smoking or not saving enough for retirement.
Source: Weinstein, N. D. (1980). Unrealistic Optimism About Future Life Events. Journal of Personality and Social Psychology, 39(5), 806-820.
Communicating risk with specific comparative statistics ("out of every 100 people like you") tends to calibrate perception better than relying only on generic warnings, which the optimistic reader tends to see as something that happens to other people.
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