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It’s the first week of 2017, and Science of Us is exploring the science that explains how people make meaningful changes in their lives. Handy information for resolution season.

If you want to make productive changes to your life — whatever those changes may be — one of the easiest yet most valuable things that you can do is to imagine that you implemented the change(s), a year has passed, and you’ve failed. What went wrong? What unexpected events arose and swept you off your path? Which parts of your goals may have been just a bit too hopeful to begin with?

This strategy is not pessimism — not exactly, anyway. Most of the world-class performers with whom I’ve had the great fortune to become close — from Olympic runner Brenda Martinez, to ultra-marathoner Karl Meltzer, to adventure racer Rebecca Rusch — tend to be optimists. And so I’ve tried to model my own mindset after theirs. Whenever I set out to accomplish something outside of my comfort zone — for example, co-author my first book, set a new personal record in a marathon, or drop those last few pounds — I do my best to approach the challenge with a positive mindset, and, in doing so, cultivate self-belief. After all, self-belief is a very real and scientifically backed performance enhancer. Without it, people are much less likely to take constructive risks and reach their full potential. Progress, and especially breakthrough, requires a good measure of optimism. In the words of Nobel Prize–winning behavioral economist Daniel Kahneman, “Confidence in future success sustains a positive mood that enhances [one’s] prospects of prevailing. When action is needed, optimism, even of the mildly delusional variety, may be a good thing.”

But at the same time, the optimism that allows us to climb mountains, start companies, qualify for the Olympics, or even just make simple life changes, like going on a diet or sleeping more, comes with at least one significant blind spot: all the stuff that could go wrong.

Normally, we don’t realize these mishaps until they derail our projects. It’s not until after the fact that we debrief, in what is commonly called a postmortem, everything that went wrong. But, according to Kahneman, this timing just doesn’t make sense. Rather than wait for things to run amok to conduct a postmortem, in his book Thinking, Fast and Slow, Kahneman writes that we should go through a “premortem” before we even start working toward our goals. (Though Kahneman credits one of his collaborators, Gary Klein, for initially coming up with the premortem concept.)

A premortem, which is beneficial for just about every endeavor, from running a marathon to starting a business, simply asks you to envision that you failed and to ask yourself: What went wrong? Or, in the words of Kahneman, “Imagine that you are [X amount of time] into the future. You implemented your plan as it now exists. The outcome was a disaster. Take five to ten minutes to write a brief history of that disaster.”

Going through this exercise not only helps to ensure that your optimism is at least somewhat grounded in reality, but it also helps you to uncover potential pitfalls on the path to your goal that might otherwise be overlooked. This way, you can prepare for them in advance. Let’s consider the two examples mentioned above.

During your marathon premortem you imagine:

• Your GPS watch conked out. (Better include at least a couple of workouts in which you run you by feel so that you’re never fully dependent on your Garmin.)

• You dropped your special sports drink and energy gels early in the race. (Why not just find out what products will be served on the course and acclimate your gut to them during training?)

• The weather was unseasonably warm. (It’s probably prudent to overdress for a few training runs so you can learn how your pacing and hydration needs change in the heat.)

• You went out too fast and hit the wall at mile 20. (Perhaps it’s worth hiring a coach to help you develop a scientific race plan based on your training paces. Or, better yet, maybe you need a coach to help you set realistic goals in the first place.)

During your start-up’s premortem you discover:

• Your main outlet for end-user awareness — for example, Twitter — crashes during your launch week. (It’s probably a good idea to diversify the means through which you reach your audience.)

• An employee who serves a critical function suddenly becomes ill or is involved in an accident. (Perhaps you should consider building more cross-training and redundancy into your plan.)

• A large and unrelated event — for instance, a terrorist attack, a natural disaster, or political upheaval — dominates the public’s attention. (How critical are early sales to your long-term success? Are there ways you can hedge against a slow start?)

Conducting a premortem is valuable — if not absolutely critical — to counterbalancing the kind of positive thinking that gives us the faith to take on big challenges and make big changes. While the premortem “is not a panacea and does not provide complete protection against nasty surprises,” writes Kahneman, “it does go a long way toward reducing the damage of plans that are subject to uncritical optimism.” (I can’t help but think that perhaps premortems should be required prior to marriages.)

It may seem like the negative thinking inherent to a premortem would work against self-belief and confidence. But if anything, it actually works toward it. When you force yourself to become aware of all that could go wrong, you become more likely to take the necessary steps to ensure that things go right. So when you set out to make productive life changes in 2017, I encourage you to adopt a positive mindset and to do what you can to nurture steadfast self-belief. But I also encourage you to write a brief history of all your future disasters. Better to endure the discomfort of a premortem than that of a postmortem.

Brad Stulberg writes about health and the science of human performance. He’s a co-author of the forthcoming book Peak Performance. Follow him on Twitter @Bstulberg.