Confirmation bias is a cognitive bias that all of us fall prey to at some point or another. Confirmation bias is about how we remember stuff. When something happens that confirms our own prejudices then we remember it but when something happens that doesn’t confirm our own prejudices then we ignore/forget about it. This can lead to superstitions, like wearing lucky socks to the football because you remember that time when you wore them and you won and not the 100s of times you wore them and they didn’t win.
A good example of this comes from alternative medicine. When someone takes an alternative remedy then they will remember the times that remedy feels like it helped them but they may forget all the times they took it and it made no difference. This leads to a false sense of the effectiveness of the remedy in the person's mind, because as far they can remember it's only ever been helpful to them.
Everyone is susceptible to these cognitive biases and it’s only by understanding and recognising them that we can limit the impact that they have on our lives.