Good times often breed complacency and scepticism of warnings. Until 2020, the public assumed pandemics were things of the past. 100 years ago, people had a better understanding of how dangerous an outbreak could be.
Carl Jung thought that an excess of something gives rise to its opposite.When there are no recessions, people get confident. Confident people take risks, leading to recessions.
Optimism and pessimism go hand in hand. In finance, we are told to save like a pessimist and invest like an optimist. The short term is full of setbacks, problems, breakages, depressions, pandemics, errors, but if you can stick around long enough, you can experience long-term growth.
The long-run is usually rather good and the short run is normally quite bad. In reconciling the two, we learn how to manage both.