Prepare for the worst possible outcome if you think it's truly necessary, but don't expect it. People understand that to expect winning the lottery is dangerous, but somehow expecting that you'll be a complete failure in life is seen as a healthier opinion. Somehow to expect that the storm will be the worst possible weather simulation is seen by many as the most true and sobering prediction, and the small chance of a sunny day as impossible, even though meterologists would reject that as a dangerous and misguided interpretation of the data.
For politics, banks, globalization, and interpretation of religious texts, some people think the worst case possible is the only case that is possible. I only suggest that they are most likely wrong.