The quote from Michael Lewis's book "The Undoing Project" highlights the mental burden of pessimism. When someone adopts a pessimistic viewpoint, they anticipate negative outcomes, which causes them to mentally rehearse the worst-case scenarios. If the feared event actually occurs, they experience the negative situation not just once but twice—first through their anxious expectations and then through the actual experience. This can lead to increased distress and anxiety, making it harder to cope with reality.

This dual encounter with negativity suggests that a pessimistic mindset can be detrimental to one's mental health. Rather than alleviating worry by being prepared for setbacks, it often results in heightened suffering. The insight serves as a reminder of the power of our outlook on life and the importance of cultivating a more optimistic perspective to improve emotional resilience and overall well-being.