Very few people are perfectly at ease. Most have something that worries them. Their kids’ education. Their job security. A big upcoming expense. A pending medical procedure. The success of a big project. You get the idea.

Their degree of agency over these things varies. Some they can’t do much about. (For example, their job could go away through no fault of their own.) But others — many, in fact — give them some agency. They can devote more time to that project, or skip that big night out so they can save money.

At some point, they’ll need to decide. How do they choose what to do? Experience plays a role; they’ve probably faced similar decision points in the past. But they must also understand the criteria that will allow them to choose one way or the other. They can inform themselves by asking friends, reading the news, or searching Google. Whatever the case, they need information.

They need more than this, though. They also need a causality model: a way to predict the repercussions of the decision. “If I do A, then Z is likely to result.” Their models mustn’t be perfect (they can’t be) — they only need offer some degree of confidence.

Leaders in organizations face many such choices, often with big stakes. These people are among the best decision-makers in the world. But creating solid models is very difficult in the complex contexts they work in. For example, a product feature may inadvertently create a national security problem. We call these unintended consequences, and they’re one of the things that keep leaders up at night.

In our complex world, we experience unintended consequences all the time. (Sometimes with disastrous results.) But there are ways we can improve our ability of predict outcomes with some degree of certainty. This is why you need to understand how systems work. Doing so allows you to learn how to model — have some control over — complex, volatile situations. It helps you sleep better.