This essay is part of a column called The Wisdom Project by David Allan, editorial director of CNN Health and Wellness. The series is on applying to one's life the wisdom and philosophy found everywhere, from ancient texts to pop culture. You can follow David at @davidgallan . Don't miss another Wisdom Project column; subscribe here .

(CNN) The plot of my only recurring nightmare goes like this: I'm back in college and have not attended one of my classes all semester (usually math or science), and now a final exam is imminent.

I'm completely unprepared, time has run out, and I don't even recall where the classroom is, so I can't find the professor. I wake up without a resolution.

This is how every brain works. It diligently perseverates over worst-case scenarios, like an anxious new parent. It's just trying to keep us safe and usually does a great job at it.

But that same vigilant hardwiring also makes it too easy to worry about the wrong things. It clouds our thinking with fear of outcomes that will never come to pass or aren't nearly as bad as we let ourselves imagine. That's the type of worry the writer Erma Bombeck equated to a rocking chair: "It gives you something to do but never gets you anywhere."

And all that useless worry is detrimental to our overall mental and physical well-being. It can misinform decision-making, raise stress levels, keep us up at night and erode our happiness.

For some, anxiety and worry are so toxic and burdensome that medication and/or therapy is needed to fully function. "What worries you," John Locke wrote, "masters you."

So learning how to better separate the good worry, which protects us, from the useless worry, which harms us, is a vital life skill.

Consider the following simple exercise to increase your insight into how much you worry needlessly. It's an experiment I did for years with the goal of better identifying and reducing my "rocking chair" fretting while better harnessing the useful kind of worry.

'Top 10 Worries'

Begin by writing down all the major things you're currently worried about. It's not pleasant to ruminate on them, but the fact is that your brain is constantly thinking about them anyway. Just because a worry is subconscious doesn't shield you from its negative effects.

I suggest two rules for making the list. First, try to make the time frame for whether they will happen just six months. That limits you to concrete and quantifiable worries. You may have general anxiety thoughts like "I think something bad is going to happen" or worries over the next year -- or four -- but for the purposes of this experiment, limit your worries to those outcomes resolved in the next 180 days.

Second, keep the number at 10. If you have more than that, pick the biggest ones. If you have fewer than 10, good for you, but challenge yourself to go deeper and find other worries of which you may be less aware.

Some of your 10 worries will be big, others small or even trivial. Some you may feel you have no control over while some you do. Don't worry about their seriousness or ranking them; just capture what's causing you any anticipatory fear.

Then, take your final list of 10, put it somewhere private and make a note in your calendar to check in on those worries in six months.

When time is up, record how many on the list came to fruition. Create a new Top 10 Worries list, and check those in another six months. Repeat the experiment until you have a better understanding of how often the things you worry about don't happen. And for those concerns that do come to fruition, you may see the needlessness of some of those worries, as well.

My score: 60% baseless worry

I performed this "Top 10 Worries" exercise many times over the course of five years. Of my 100 total worries, 60 didn't happen. That's a lot of needless attention, and I could have used that time in better ways.

Here is what I also learned: That percentage of wasted worry went down as the experiment went on. In other words, more of the things I worried about actually happened.

During the first few rounds, about 80% of my worries were as illusory as my college class nightmare. But over the course of the experiment, I more accurately anticipated bad outcomes because I got better at not worrying over what was highly unlikely (and not because my life got increasingly unlucky over those years).

It also became harder to make lists of 10 over time, because the experiment itself was reducing worry.

Even more edifying was that of the 40 worries that did occur, most of them fell into two categories: Either they happened but didn't seem nearly as bad as I worried they would be (such as needing to dip into savings), or they happened but there was nothing I could have done to prevent them (such as whether a friend broke up with his significant other).

Both of those worry types, even though they made the leap to reality, were also pointless.

The idea that some circumstances we call "bad" can, over time, turn out favorable is a Taoist philosophy I've written about before. Sometimes, there is a big upside to what seemed bad (such as a horrible breakup that leads to finding your true love). And the wisdom of knowing the difference between the things you can and can't change is famously covered by the words of pastor Reinhold Niebuhr's Serenity Prayer . Recognizing those two kinds of needless worries is just as helpful as learning that we too often worry about fiction.

Looking back at my 100 worries, if I take away what never happened, what wasn't so bad and what was out of my control, all that remained were a handful of worries that seemed useful. Some came true, some remained negative, and some I could have done more to change the outcome (e.g. not getting a particular job offer or opportunity I wanted).

By clearing your mind of needless worry, you can hone in on the real concerns you might be able stop. And even if you can't stop them, there's value in occupying your mind with action over fear. As actress Angela Lansbury put it, "better to be busy than to be busy worrying."

What, me worry?

"One thing life taught ye was how stupid it was to worry about things ye didnay know for sure, things that might no even happen, nay point in worrying about them," wrote the Scottish novelist and playwright James Kelman.

You may need to teach yourself the same lesson, and tracking your worries can be an effective way to do it. It could be more helpful to you to make your list longer or shorter than 10, or to have a longer or shorter time frame than six months, but make it quantifiable so you can be a bit scientific about it.

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Convincing yourself that you worry too much about unlikely outcomes or about things beyond your control is one way to retrain your brain to worry less and worry smarter.

I concluded my personal experiment, and it didn't free me from all worry, of course. But I worry less often and about fewer things.

Now, when a worry starts to brew in my mental cauldron, I take a hard look at whether it's just fictional preparedness, whether there may be something good that could come if it does happen and whether I can do anything to prevent it.

If the answer is "yes" to any of them, I can more easily leave that rocking chair empty.