Choice-supportive bias is a cognitive bias where people tend to retroactively view their decisions as being better than they objectively were. It involves selectively remembering positive aspects of the decision and downplaying (or forgetting) negative aspects. It can also include exaggerating the negative aspects of alternative choices.
This bias is a way to reduce cognitive dissonance and maintain cognitive consistency. It’s psychologically easier for us to believe we’ve made the correct decision than it is to acknowledge flaws in a choice we’ve already committed to.
Examples
Purchasing a car. After buying an expensive car, we’re more likely to focus on its favorable features to justify the purchase than we are to admit that it was outside of our budget. We might also exaggerate the downsides of the other cars we were considering buying.
Hiring an employee. A manager who hires a new employee might downplay the employee’s shortcomings and focus instead on their successes (even if the shortcomings outnumber the successes). The manager might also exaggerate the potential downsides of the candidates not hired.