Hindsight bias is a psychological phenomenon that can have profound impacts on decision-making and lead to costly errors. It is a cognitive bias in which individuals incorrectly assume that they predicted an event before it happened, and then interpret the actual outcome as having been predictable all along. This type of biased thinking can cause an individual to place too much confidence in their own ability to make accurate predictions in the future and end up taking unnecessary risks.

Let's take a look at an example of how the bias works. Suppose an investor buys Apple stock right before it doubles in price, and then looks back and claims they "knew" the stock was going to do well. In reality, they had no way of knowing the stock would be a success – their prediction was simply the result of hindsight. They didn't actually predict the price increase – it was a lucky guess.

This kind of biased thinking can be damaging, specifically because it creates an illusion of certain predictability. As such, investors may become over-confident in their ability to accurately predict future events, leading them to undertake unnecessary risks that may prove costly.

The best way to avoid hindsight bias is to document the decision-making process. This can be done through the use of an investment diary or similar method of keeping track of all decisions made. By taking the time to document the reasoning and research behind each decision, an investor can ensure that future decisions are based upon fact and evidence, as opposed to biased thinking.

Overall, hindsight bias is a pervasive cognitive phenomenon that can seriously impair decision-making. To prevent bias from influencing one's decisions, it is important to carefully document the reasoning behind each investment and always stay alert to potential decisions that might be motivated by over-confidence or biased thinking. By taking these simple precautions, investors can ensure that they are not swayed by the illusion of certainty in a future they cannot predict.