I’m going to talk to you about optimism – or more precisely, the optimism bias. It’s a cognitive illusion that we’ve been studying in my lab for the past few years, and 80 percent of us have it. It’s our tendency to overestimate our likelihood of experiencing good events in our lives and underestimate our likelihood of experiencing bad events. So we underestimate our likelihood of suffering from cancer, being in a car accident. We overestimate our longevity, our career prospects. In short, we’re more optimistic than realistic, but we are oblivious to the fact.

https://www.ted.com/talks/tali_sharot_the_optimism_bias