There are a number of ways in which our thinking can go wrong. One of these are mistakes due to what are known as cognitive biases. These are mistakes that the brain is hard-wired to make. It might seem odd that the brain is set up to make mistakes, but of course it evolved to solve the problems and challenges that would have confronted our distant ancestors living as groups of hunter-gatherers. These would in all likelihood have been problems concerned with immediate short-term survival such as finding food, shelter, avoiding dangerous predators as well as living long enough to find a mate and to procreate.
In the rich west, we have largely solved these kinds of problems, but we still inhabit the same brains and bodies as early humans. We are therefore not designed to solve the difficult reasoning problems that confront us now. Our brains take short cuts and arrive at quick. effective and practical solutions. Thinking through abstract problems is not really what they are designed for and we are lucky that we can do it at all.
An area where our brains let us down is thinking about risk and probability. One aspect of this is reflected in the kinds of stories that are covered by the news media. They give disproportionate coverage to one-off events that result in large numbers of deaths, such as plane crashes, while ignoring the fact that more deaths occur in car crashes because each individual car crash is responsible for only one or two deaths.
This can lead to poor decisions. After plane crashes more people drive. This actually increases risk. It is much more likely that we will be killed driving to the airport than on the plane to our destination. It also distorts government policies. Since these large accidents are more newsworthy, they garner attention and politicians, responding to what is in the news, feel pressured to act. If they acted rationally, however, they would respond to the greatest threats to life rather than the most newsworthy ones.
Another point worth noting is that accidents, terrorist atrocities, even wars, while tragedies for the individuals involved, have virtually no effect on humanity as a whole. The only day this century that the human population has not risen was the day of the 2004 Indian Ocean tsunami in which 230,000 people died. The human population is currently rising at about 75 million people a year or 205,000 a day. This means that none but the most extreme events have any noticeable effect on the number of people on the planet.