We were all going to die. It was pretty scary to look up in the sky and see so many spaceships flying around blowing things up. I was also afraid that some of the aliens were on the ground, hunting us down. Where were they? Were they after me?!
That nightmare had me in a funk all day.
The next night I was reluctant to go to sleep because I didn't want to have another bad dream. But I very rarely have them. If I think about it rationally, and think about the statistics, the chances of my having a nightmare on any given night is extremely low.
But the powerful and memorable bad dream was front and center in my brain. It took over and clouded my perception about what was to come.
The point is - we have a tendency to let memorable experiences shape our expectations. It's what we do (see here to learn about the availability heuristic). We have to override it, or at least try to.
When we make decisions - even rationally - we try to predict what will happen if we choose each option. If those predictions are off because we rely too much on memory, our entire decision-making is off.
So next time you're making an important decision, beware of relying on memory to decide what to do. Try to look for objective evidence of how likely an outcome might be. Ask yourself what you don't know, what you can learn about or research that you haven't yet. And use all that knowledge when you make your decisions too.
It's the least you can do to sleep well at night.