It plays on this tendency of ours to emphasize loss over gain.

The term sunk cost refers to any cost that has been paid already and cannot be recovered. The reason we can't ignore the cost, even though it's already been paid, is that we're wired to feel loss far more strongly than gain.

It is a glitch in our thinking that occurs when we place too much weight on past events, believing that they will have an effect on future outcomes.

This is when we mistakenly think that eventually, our luck has to change for the better.

Somehow, we find it impossible to accept bad results and give up—we often insist on keeping at it until we get positive results, regardless of what the odds of that happening actually are.

It happens when we rationalize our purchases, even if we're not satisfied with what we've got.

It essentially works like this: rather than making a decision based on pure value for investment (time, money, etc.), we factor in comparative value—that is, how much value an option offers when compared to another option.

We believe our memories more than facts. Our memories are highly fallible and plastic. And yet, we tend to subconsciously favor them over objective facts. 

Don't base a factual decision on your gut instinct without at least exploring the data objectively first.