Why does Mark Zuckerberg always wear the same thing every day, or President Obama only dress in one color suit?

Because both are leaders whose days are filled with weighty and difficult decisions, and because as the hours tick by our decision-making capacity is worn down. Making one less choice about what to put on in the morning means both men have just a little more mental horsepower to make thoughtful calls later.

A clear mind and even emotions are scarce resources, in other words, and generally as we go through our day we have less and less of them at our disposal. But wouldn't it be great if you could get back a little bit of the clarity and calm you started with even though you're on your fourth meeting of the day? Is there any way to accomplish such a thing beyond an incredibly boring wardrobe?

Yes, suggests a recent HBR blogs post by Chade-Meng Tan, who leads a Google training initiative called "Search Inside Yourself." It's "designed to help people put down... mental baggage and approach each new situation with a present, focused mind," he explains, adding that "it quickly became the most highly rated course in all of Google."

Tan's piece goes into detail on several of the strategies he teaches, but one in particular stands out as both effective and dead simple. And what's even better, it'll only take six seconds of your day to accomplish.

Try this before your next meeting

How could something that takes less time than an Olympic 100-meter dash make such a difference? Tan offers the example of Karen May, a VP at Google. She has "developed the ability to mentally recharge by taking one 'mindful breath' before walking into every meeting. It takes her roughly six seconds, and in that time she brings her full attention to one breath, resetting her body and mind," he explains.

We all breathe all day long so how could simply paying attention to one inhalation have such a big impact? Tan offers two explanations: "The physiological reason is that breaths taken mindfully tend to be slow and deep, which stimulates the vagus nerve, activating the parasympathetic nervous system. It lowers stress, reduces heart rate and blood pressure, and calms you down."

"The psychological reason is that when you put your attention intensely on the breath, you are fully in the present for the duration of the breath. To feel regretful, you need to be in the past; to worry, you need to be in the future. Hence, when you are fully in the present, you are temporarily free from regret and worry," he continues.

If you're not totally convinced that something so simple could really recharge your mental resources and improve your decision-making ability, Tan notes that the technique isn't just used by tech executives, but also by great athletes like Novak Djokovic.

Something similar has also been recommended by a very different sort of expert here on Inc.com previously. Meditation teacher and author Sharon Salzberg noted that incredibly simple "stealth mediations" such as just savoring a cup of tea can make leaders much more clear-headed and effective.

Do you have six seconds to take just one mindful breath (or sip) before your next meeting? (Of course you do!)