An entrepreneur just might have been Tom Petty's muse when the singer set to music something small business owners know all too well: The waiting is the hardest part. 

Whether you're waiting to hear back from that angel investor; waiting to find out if the dream client accepts your proposal; or waiting on word from a top-pick potential hire who's choosing between you and your competitor, playing the waiting game takes up a big chunk of small business time.

And waiting usually means worrying: Did I do enough? I wish I hadn't done that. Should I have done more? I can't believe I said that.

It's tough to avoid those what-if scenarios, especially when the waiting involves a result you really want. But a recent study published in the journal Personality and Social Psychology Bulletin and funded by the National Science Foundation shows the practice of mindfulness can help take the worry out of waiting.

Since mindfulness involves paying full attention to the present moment, rather than ruminating on the past or fretting about the future, it makes sense that the practice can ease stress associated with uncertainty.

So when you find yourself waiting--for a result, for a response, or even for a traffic jam to thin out--try these two mindfulness techniques to help tame the tension of anticipation.

1. Practice Square Breathing

One of the quickest, easiest ways to calm your mind and come back to the present moment is through mindful breathing. It sends more oxygen to your brain, increasing focus and decreasing distraction.

Mindful breathing not only lowers your stress level, but also lowers your blood pressure and heart rate, according to a 2005 American Heart Association study in the journal Hypertension. One of my favorite mindful breathing techniques is square breathing, also known as box breathing. Here's how to do it:

Inhale slowly through your nose while counting to four. Gently hold the breath for a count of four. Slowly breathe out through your mouth for a count of four. And then gently hold the breath for a count of four. 

Repeat as many times as you'd like.

When I'm waiting in a slow line at the grocery store and haven't build in enough of a buffer to get to my next meeting, square breathing is my go-to.

If it helps, you can visualize one line of a square being drawn for each count of four. You can even draw the lines on paper as you count. I taught my teenage son this trick, since he's more of a visual learner. It's a great tool for kids to use in times of stress.

Worrying can cause shallow breathing, so controlling and focusing on the breath brings your respiratory and nervous systems back into alignment.

2. Do a Body Scan

Waiting and worrying keeps you in your head, where there's fertile ground for rumination and runaway thoughts. So grounding yourself back into your body is key to centering yourself and reducing anxiety. 

The next time you're stressed out while waiting for something, try asking this question: Where is the worry showing up in my body?

A 2013 study by brain researchers at a University in Finland revealed that emotions show up as physical symptoms. Bringing your full attention to those symptoms helps get you out of your head and back into the present moment.

Sometimes, when you're looking for your worry's physical location, the answer will be immediately clear: sweaty palms or a racing heart, for example. But if you're not sure, you can do a body scan to find out where you're holding tension.

Begin at the top of your head and work your way down, noticing any spots of tightness. Is your jaw clenched? Is your chest tight? Maybe you notice an upset stomach or tingly legs?

Rather than letting your head run away with a thought, you're allowing your body to experience a feeling.

The goal is to simply let that feeling in, rather than make it go away. You're leaning into the discomfort, rather than trying to avoid it.

I used this technique recently while waiting to hear from publishers who were considering my book. When I found myself in my head, worrying about possible rejection or wondering whether their silence was positive or negative, I scanned my body and consistently discovered tightness in either the back of my neck or my shoulders.

Once you locate the tension, just feel it. Sometimes I take a deep breath into the spot of tightness, which helps it soften. Keep in mind your only goal is to become conscious of where the worry is showing up in your body.

That physical awareness will take your racing mind out of the equation, grounding you in the here and now, and helping you win at the waiting game.