Illustration: Cecilia Martin

The world can be divided in many ways, and one is between optimists and pessimists. The other day, Molly Fisk wrote, in “Benign Outcomes,” that even beyond this character trait, which is to some degree inborn, many of us are influenced by our negative past experiences to expect them to be repeated. In most cases, we are not even aware that we are doing this, since these memories are unconscious. Psychologists and psychoanalysts know that the unconscious is “atemporal.” In the world of the unconscious, it is always “now.”

That’s why so many of us react in situations that recall past trauma as if we were still helpless and small. When they happened, that’s usually exactly what we were, and in our mind we have not “caught up” to the present reality of being a competent adult.

So, for example, a woman in her 40s who experiences the anger of another woman as debilitating and is undone when she gets into conflicts with her contemporaries is reacting, at least in part, to her abusive mother, who used to berate her and hit her with her hairbrush when she was angry. This woman needs to constantly remind herself of the present reality that she is an adult who is not helpless and trapped by a frightening, bigger person who has all the power.

RELATED: Molly Fisk: The Power of Anger; or, Hexed by a Bear

But what about the rest of us who suffer from garden-variety pessimism? There’s an awful lot to worry about, and even those of us who were not specifically abused may not have been made to feel particularly safe. Add to that the theory of evolutionary biologists that the worriers among us may have survived at a higher rate than did the happy-go-lucky types. In theory, our ancestors who lived out on the dangerous savannah would have fared better if they had been watching for the possibility of attack by lions and tigers and bears than if they decided to forget about it.

But forgetting about it some of the time is necessary to survive in peace—it’s called “healthy denial.” If you worried about every possibly dangerous situation or thing that could go wrong during the course of your day, you would never leave the house. This capacity for healthy denial is part of what terrorists target when they attack. They provoke the fear—a fear we all know is somewhat true—that anything can happen, anytime, anywhere.